Amphibian water quality: approaches to an essential ......2019/02/23 · effective at removing...

Int. Zoo Yb. (2008) 42: 40–52

DOI:10.1111/j.1748-1090.2008.00053.x

Amphibian water quality: approaches to anessential environmental parameter

R. A. ODUM1 & K. C. ZIPPEL2

1Toledo Zoological Society, Toledo, Ohio 43614, USA, and 2Amphibian Ark/CBSG,Apple Valley, Minnesota 55124, USAE-mail: [email protected]

Appropriate water quality is essential for maintaining andbreeding amphibians in captivity. Aquatic systems thatmaintain water quality have been employed for manyyears in the aquaculture and aquarium industries. Thesetechniques are now more commonly being utilized foramphibians. Using information from the work of theauthors and published literature on amphibians and fish,benchmarks are provided for common water-qualityparameters for amphibians.

Key-words: amphibian; benchmark; breeding; water-quality parameters.

INTRODUCTION

Long relegated to a footnote in many reptilefacilities, it is only recently that amphibianshave been receiving the attention they de-serve from zoos and aquariums. Unfortu-nately, this attention was slow in coming andwas only in response to the urgency of thecurrent extinction crisis facing the entireclass. In reaction to the crisis, the zoo com-munity, IUCN – The World ConservationUnion and other conservation organizationshave inaugurated a response to create captivesurvival-assurance populations to preservethreatened species and to allow the option offuture reintroductions, if necessary (Pavajeauet al., in press).

Regrettably, it has quickly become appar-ent that there are many more taxa in need ofhelp than there are facilities capable of pro-viding assistance. Although zoos have had agreat deal of experience with the amnioticterrestrial vertebrates, few have had a longhistory with amphibians. Most taxa havenever been maintained in captivity and, ofthose that have, most have not been bred.

Dendrobatidae are the most common captive-bred anurans in zoos (ISIS, 2007).

There are critical differences betweenthe husbandry of amphibians, which havethe most diverse reproductive strategies, andthe other tetrapod vertebrates (reptiles, mam-mals) (Duellman & Trueb, 1986). Their skinsare highly permeable, making them prone todesiccation and absorption of environmentalpollutants directly through their skin. Perhapsthe most descriptive metaphor that best de-scribes the amphibians is, ‘Think of theseanimals as fish with legs’. Fish are managedin captivity by providing them with a cleanand appropriate water environment; this isexactly the same way in which amphibiansshould be managed.

Any supply of water for amphibians mustmeet certain minimal requirements to main-tain the health and normal physiology of theanimals (Schmuck et al., 1994). Water fromeither a natural source or a treated source (e.g.municipal water supply) is not a pure sub-stance, but a suspension and solution ofvarious organic and inorganic components.These additional substances in the watermight be required to maintain the organism,might have no effect or might be detrimental.Amphibians have invaded many differentniches, and the individual water requirementsfor a given species and its tolerance tospecific toxins vary. It should be noted thatdifferent life stages of an amphibian may alsohave different requirements. The overall con-centrations of these substances and sus-pended material in a supply of water areconveniently grouped together under the term

40 AMPHIBIAN CONSERVATION

Int. Zoo Yb. (2008) 42: 40–52. c� 2008 The Authors. Journal compilation c� 2008 The Zoological Society of London

‘water quality’. This includes all aspects ofthe water (e.g. pH, inorganic salts, organiccompounds, metabolic waste products, dis-solved gases and bacterial suspensions).

This article is a brief overview of waterquality as it relates to amphibian husbandry.Most of the techniques presented have beendeveloped by the aquarium and aquaculturecommunities to maintain and reproduce fish(Stickney, 1979). These have been success-fully adapted by some institutions to maintainand breed amphibians. The key to thesesuccesses is in part owing to an appreciationand knowledge of water quality and thesystems necessary to maintain high-qualitywater (as well as an understanding of thebiology of the animals we maintain). Clearly,water quality is far more important for thoseanimals that spend most or all of their time init (e.g. larvae larviforms and other aquaticadults), but even for those who might onlyrely on terrestrial substrate moisture, waterquality is an essential factor for health of theanimal.

PARAMETERS FORWATER QUALITY

Extensive work has been carried out in thefield of aquaculture to quantify the relation-ship between water quality and the health offish and some aquatic invertebrates (Envir-onmental Protection Agency, 1976). In con-trast, the published literature for amphibiansis relativity scant.

Table 1 shows some common parametersfor the water quality for amphibians. Theseparameters were developed from the pub-lished literature for amphibians and fish, aswell as the direct experience of the authors.These are only guidelines. The tolerance tocommon toxins and the requirements for eachspecies are still unknown for the majority ofamphibian taxa. Therefore, these suggestedlevels should be considered only for guidancein evaluating system performance.

Water sources

Water is available from many sources foramphibian husbandry, and water quality ofthese sources varies extensively. A first step

in evaluating a water supply is to performappropriate tests for dissolved substances, pHand hardness. At least initially, it is veryuseful to have your water source tested by alaboratory qualified for this purpose. MostUS counties or states provide water-testingservices for water supplies intended for hu-man consumption, and there are also manycommercial laboratories that provide theseservices at a reasonable cost. The results ofthese tests will help to identify any pretreat-ment that is necessary for the water before itcan be utilized for amphibians. The humanpotable water standards (less disinfectants)are a good start for evaluating water supply.If you would not drink it, then it is probablynot the best water for your animals.

Many amphibian facilities use a local mu-nicipal water source for their operations, butsome preconditioning of the water is almostalways necessary. Municipal water is usuallydisinfected with free chlorine (Cl2) or chlor-amines. Eliminating these disinfectants is afirst step in pretreating water. If free chlorineis the disinfectant, simply ageing and aeratingtap water for 24 hours is all that is required tocondition it for use with amphibians. Aera-tion will also drive off other harmful gases(carbon dioxide, nitrogen, hydrogen sul-phide) and bring desired gases (oxygen) intoequilibrium between the water and the atmo-sphere.

If chloramines are used as a disinfectant inthe water supply, this ageing process is in-effective. The chloramines need to be re-moved through chemical filtration or throughchemical treatment. Activated carbon is lesseffective at removing chloramines than freechlorine from water. There are commerciallyavailable filters specifically designed to re-move chloramines that contain carbon andadditional media. To remove chlorine chemi-cally, create a saturated solution of sodiumthiosulphate (Na2S2O3) in water by adding itto a small volume of water until no morechemical will dissolve (note that Na2S2O3

is usually available as a pentahydrateNa2S2O3 � 5H2O, which is suitable for thisapplication). This solution can then be usedto dechlorinate water by adding one drop of

WATER QUALITYAND AMPHIBIAN CONSERVATION 41


WATERQUALITY

PARAMETER

EFFECTONAMPHIBIA

NS

ACCEPTABLELEVELS

METHODSOF

ALLEVIATIO

NCOMMENTS

REFERENCES

Water

hardness

(dissolved

Ca

andMgsalts)

Hardwater

cancauseskin

problemsin

somespecies

bydisrup

ting

norm

alosmoticregulation

ofthe

amphibian.Mostsho

wa

preference

for‘softwater’

butthiscanbe

species

depend

ant

o75

mglitre�1(ppm

)of

CaC

O3foranim

alsthat

requ

iresoftwater

410

0mglitre�1shou

ldbe

considered

hard

water

foran

amphibian

Dilutinghard

water

withRO,D

Ior

distilledwater

Hardening

soft

water

withCaand

Mgsalts(only

recommendedfor

reconstituting

RO,

DIdistilledwater)

Whitaker(2001)

Dissolved

oxygen

asO2

Oxy

genisneeded

for

amphibianrespiration

andaerobicprocesses.

480

%Saturation

Aeration

Som

eanuransand

salamandersmay

beableto

toleratevery

lowlevelsof

oxygen

Gulidov

(1969);

Brung

s(197

1);

Carlson

&Siefert(197

4);

Siefert&

Spo

or(197

4);

Siefertetal.(19

75);

Odu

metal.(19

84);

Whitaker(2001)

Gas

supersaturation

Gas

bubb

ledisease

Gases

should

beat

equilibrium

with

atmosphere

Aerationun

til

equilibrium

isachieved

Com

mon

inwellwater

and

pressurizedmunicipal

water

sources,especially

whencold

Ammon

ia/

Ammonium

–NH3/NH41

Verytoxic

o0�2

mglitre�1,

Nas

unionized

ammon

ia

Biologicalfiltration,

chem

icalfiltration

withappropriate

medium,o

rwater

changes

Metabolicwasteproduct

Ammon

ia/ammon

ium

ratioispH

and

temperature

dependant

(see

Table2)

Tabata(196

2);

Herbert&

Shurben

(1965);

Ball(196

7);

Jofre&

Karasov

(1999);

Rou

seetal.(19

99);

Whitaker(2001)

NitritesNO2�

Tox

ico1�0

mglitre�1,

butideallyzero

Biologicalfiltration,

chem

icalfiltration

withappropriate

medium

orwater

changes

Aproductof

aerobic

biologicalaction

onam

mon

iaNH3/NH41

Kling

ler(1957);

Russo

etal.(19

74);

Westin(1974);

Marco

etal.(19

99);

Whitaker(2001)

NitratesNO3�

Slightlytoxic

o50�0

mglitre�1

Rem

oveby

photosyn

thetic

action

ofgreen

plantsandby

water

changes

Thisistheendprod

uctof

biologicalfiltration

Westin(197

4);

Whitaker(2001)



PH

Can

causemetabolic

problemsifno

twithin

acceptablerang

efor

species,disruptsion

exchange

Species

dependant,bu

tusuallynear

neutral.

pHbelow6andabove

8arepo

tentiallyaproblem

Changewater

source

oraddappropriate

buffers

Cum

mins(1989);

Warneretal.(19

91);

Whitaker(2001)

ChlorineCl 2

Verytoxic

0Aeratefor24

hours

oraddchem

ical

dechlorinator

(e.g.sod

ium

thoisulphate)

Som

eadultform

sseem

tobe

ableto

toleratechlorinated

water:Ceratophrys

ornata,R

anacatesbeian

a,Ambystom

atexanu

m,

Ambystom

atigrinum

,Litoria

caerulea,

Ichthyop

hiskohtao

ensis

Arthu

r&

Eaton

(197

1);

Culley(199

2);

R.A.O

dum,pers.ob

s

Chloram

ines

(ClNH2,C

lN2H,

ClN

3)

Verytoxic

o0�01mglitre�1as

Cl

Use

chem

ical

treatm

entspecific

forchloramines

(e.g.P

rime)

Sim

ilar

toCl 2in

toxicity,but

also

releases

ammon

iaEnv

iron

mentalP

rotection

Agency(197

6)

Copper(Cu)

Tox

ico0�05mglitre�1

Carbonfilteringand

carbonate

precipitation

Dono

tuse

copper

pipes

Copperwater

supply

pipes

canbe

flushedbefore

collecting

water

Pritchard-Lande

&Guttm

an(197

3)

Phosphates(PO43�)

Toxicto

manyanim

als,

interferes

withcalcium

metabolism

Toxicitymay

bespecies

specific.EPA

limits

PO43�to

10mglitre�1.

Applicationsof

1mglitre�1are

considered

effective

forpreventing

pipe

corrosion

Pho

sphatesponges

andfiltersare

availableto

absorb

phosph

ates

Atelopu

ssppadultsseem

tobe

particularly

sensitive

toph

osph

atetoxicity

Tab

le1.

Water-qualityparam

etersformaintenan

ceof

amphibiansin

captivity:DI,de-ionized;DO,dissolved

oxygen;EPA,EnvironmentalProtectionAgency;

RO,reverse

osmosis.



the saturated thiosulphate solution for every4 litres of water. Care must be taken not to usetoo much sodium thiosulphate (beyond thesaturated solution dose as described here)because it can be toxic. Also, the chemicalreaction between thiosulphate and chlora-mines leaves free ammonia in the water,which is a significant toxin that needs to beremoved (Smith, 1982).

Another common source used in facilitiesis well water. Well water can be an accepta-ble, consistent source of water for use withamphibians but again one must test for pH,hardness, metal content and, in coastal areas,salinity. In some regions, especially wherewater is pumped up from limestone bedrock,well water can be too hard and the pH toohigh – test and treat accordingly. In agricul-tural areas, well water can also be high inphosphates (PO4

� 3) and nitrates (NO3� 1)

from fertilizers that seep into the aquifer.These substances cause algal blooms, and athigher concentrations are toxic to animals.

Well water can also be supersaturated withnitrogen and carbon dioxide, devoid of oxy-gen and can even contain lethal quantities ofhydrogen sulphide. Vigorously aerating thewater for at least a day before use will driveoff the nitrogen, carbon dioxide and hydro-gen sulphide, as well as raise the oxygencontent. Aeration can also help precipitatesome compounds (i.e. iron) before the waterenters the animal enclosure.

Rainwater has also been used for captiveamphibians. This resource can be a solutionin isolated facilities that do not have otherwater supplies available. Rain water is natu-rally soft, perhaps too soft for some species(see reconstituting water below). Test for pHif air pollution is a consideration (acid rain).Also, one must consider how the rain iscollected. Do not collect rain from a galva-nized steel roof or one that has otherwisebeen treated chemically.

Water that collects in natural basins, suchas ponds, streams and lakes, can be a goodsource of acceptable water. One must checkwhere the water is coming from; for example,is it draining from a large parking areacovered with oil spills, or from a farmer’s

field where it might have picked up fertilizers,herbicides or insecticides? Another thing toconsider is that this water might be contami-nated with diseases or parasites from wildanimals. If the source is in an area wherechytrid fungus Batrachochytrium dendroba-tidis is present, the water source should bescreened for its presence. Alternatively, the‘stuff’ living in the water could be beneficialfor the care of the animals, particularly smalllarvae. Natural pools teeming with inverte-brate life offer more diversity and nutritionthan could ever be cultured artificially. One ofthe authors (R.A.O.) was successful onlyafter multiple attempts to rear filter-feedingBanded rubber frog Phrynomantis bifasciatuslarvae by using pond water containing largeamounts of green algae and protozoa. Ofcourse, an unfiltered natural water source isnot appropriate for biosecure situations. Suchsources would have to be filtered and disin-fected to assure that no pathogens are intro-duced into a biosecure colony of amphibians.

If tap water is not acceptable and a reliableoutdoor supply is unavailable, bottled watermight be an acceptable alternative. Again, thepH and hardness, and even the chlorine level,must be tested. Bottled spring water pumpedup through bedrock can be unacceptably hardand basic. Furthermore, purity-testing re-quirements for bottled water are not as strictas for tap water. A recent survey by theNatural Resources Defense Council (NRDC)showed that one in three samples of bottledwater contained contaminants, including syn-thetic organic chemicals, coliform bacteria oreven arsenic. In some cases, bottled ‘spring’water was shown to be simply filtered bottledtap water. Consult the NRDC website orwrite/call NRDC Headquarters, 40 West20th Street, New York, NY 10011, USA(Tel:11-212-727-2700), to get the results fora particular bottled water source.

If the water supply in a facility has highlevels of copper or other contaminants thatcannot be addressed by other means, reverseosmosis (RO) water should be considered as apossible solution. This can be a safe andconsistent way to ensure a constant supply ofvery pure water, which in itself creates other



problems. Like rain water and distilled water,RO water is essentially pure. In fact RO wateris, in many cases, too pure to be used as it is.It may be used for species that normally livein pure rain water, such as some dendrobatidsand other phytotelm (water accumulated intree holes and plants such as bromeliads)dwellers. For many other species, chemicals(salts for osmotic issues and trace elementsfor health considerations) need to be added.Common symptoms of osmotic imbalancecreated by too pure water include bloatingand kidney dysfunction.

Commercial additives containing the re-quisite trace elements are available. A simplepreparation to reconstitute RO water is listedbelow. This mix was developed largely byfish and aquatic plant hobbyists, and fine-tuned for amphibians.

In 100 litres of RO water dissolve:� 4 � 0 g calcium chloride CaCl2� 4 � 6 g magnesium sulphate MgSO4 � 7H2O� 3 � 6 g potassium bicarbonate KHCO3

� 3 � 0 g sodium bicarbonate NaHCO3

� 0 � 13 g commercial trace-element mixDissolving the crystals in a jar of water first

and then adding the solution to the storagetank will ensure proper mixing. The finalcomposition is similar to moderately softfresh river water, with roughly 31 generalhardness and 21 carbonate hardness, idealCa:Mg (3:1) and Na:(Ca1Mg1K) (1:4) ra-tios, and depending on aeration levels, a pHaround 7 � 4. The trace-element mix providessmall quantities of elements that are usuallypresent in low concentrations in most bodiesof water. Trace-element mixes are availablethrough hydroponics suppliers (e.g. Home-grown Six Pack, Homegrown Hydroponics).

RO filters do not remove everything. Somenitrates, phosphates and silicates, which canbe present in tap water at low concentrations,can pass through. Although not toxic at lowlevels, these substances can cause unsightlyalgal blooms. A de-ionizing (DI) filter car-tridge used in conjunction with the RO filterwill help eliminate nitrates and phosphates,should they prove problematic. A DI filteruses chemical resins that must be periodicallyregenerated or replaced.

Designing water systems for amphibians

Two general types of aquatic system arecurrently used to house amphibians in collec-tions – the open system and the semi-closedsystem. The open system allows fresh, cleanwater to enter the enclosure, at a flow ratewhereby the water remains within the enclo-sure for a short period of time and is thendischarged. This flowmay be established by avariety of methods, including misting, spray-ing and direct influx of liquid water. It may becontinuous or intermittently added (i.e.timer). In semi-closed systems, a quantity ofwater is added and removed periodically (e.g.weekly or monthly) as a percentage of thetotal water volume in the system.

The open system is one in which water andother matter, food and energy, are continuallyentering (influent) and leaving (effluent) theenclosure. Waste products, organic toxins,decaying organic matter, dead food items,inorganic compounds, etc, are flushed fromthe enclosure, and the water quality is main-tained as long as the rate of influent flow issufficient. No type of enclosure filtration isneeded because the water is never in theenclosure very long. In theory, open systemscan be the least complicated, most mainte-nance-free type of system. Another benefit tothese systems is that potentially pathogenicorganisms do not build up within the enclo-sure because they are continually removedwith the effluent. The main problem withsuch a system is having a continuous suffi-cient supply of appropriate quality (and tem-perature) water. Open systems are commonlyemployed in large aquaculture operations,such as fish hatcheries, where large quantitiesof water are pretreated before they are used.

The most common type of aquatic systemused by the aquarist to maintain water qualityis the semi-closed system. What has beenlearned in the aquarium field has been suc-cessfully adapted for use within amphibianenclosures at many institutions. Incorporatingmechanical, chemical and biological filtrationwith the occasional partial water change inamphibian enclosures has greatly reducedmortality and has facilitated successful



breeding of several species. However, theopen system has many benefits for maintain-ing water quality and reducing pathogens,while reducing system complexity, oversemi-closed systems.

The materials used to construct any watersystem are important. Metallic containers,vessels and piping should be avoided. Inparticular, copper pipes leach copper into thewater and should be avoided, in both thesupply lines and filter systems. InexpensivePVC piping is easy to install and has few ofthe negative aspects associated with metalpiping.

There are a variety of specialized plumbingfittings that simplify the construction of anaquatic system, as well as adding flexibility.In particular, bulkhead fittings have a lot ofpotential uses because they connect theplumbing to the inside of an enclosure. Thispiping can be used to provide influent, filtra-tion or drainage to the tank. Pipes come in avariety of nominal sizes and can be adapted tosmall or large systems.

Filtration

In semi-closed systems, water quality ismaintained by continually treating the waterwith a filter system. There are three basictypes of filters employed for aquatic husban-dry: mechanical, chemical and biological. Itis a good idea, in semi-closed systems, toincorporate all three filter types to maintainappropriate water quality. It should be notedthat although each filter type has its specificfunction, it is not uncommon for a filter toperform several functions simultaneously.

For small volumes of water, wad-type andcanister filters are commonly employed formechanical filtration. These small units canbe very effective in maintaining water clarityand may also provide other types of filtrationfunctions. The medium used in wad filters is aclump or a pad of polyester wool, which isinexpensive and easily obtained. Many typesof cartridge mechanical filters have becomeavailable commercially for aquatic systems(see Plate 1). These filters employ a manu-factured cartridge element that is available in

different grades that correspond to the smal-lest particle size they will remove. Pressur-ized water is forced through the cartridgewhere the particulate is trapped. Both thesetypes of filters will clarify the water effec-tively but fail to remove micro-organisms thatcould be pathogenic. At best, this type offilter will remove small filter-feeding organ-isms but not their food (Wickins & Helm,1981).

It should be noted that while other types offilters (e.g. chemical and biological) can alsoremove particulate, this is not their primaryfunction. In many cases, the ability of theseother types of filters to remove particulateinhibits their primary function and greatlyreduces their efficiency. To prevent this pro-blem, a mechanical filter should be employedto remove the particulate so that the operationof the other types of filters is uninhibited.Such mechanical filters are commonly incor-porated into filter-system designs.

The earliest mechanical-filtration systemsdeveloped are the slow and rapid sand filters.These filters utilize fine sand as the filtermedium, are more efficient than the wad-type

Plate 1. A common design for a canister filter. De-pending on the media installed, these filters canprovide mechanical, chemical and even biologicalfiltration. R. A. Odum, Toledo Zoological Society.



filters and can remove particles effectivelydown to c. 6 mm with a sand diameter of0 � 3mm (manufacturer’s data). The slowsand filter functions by gravitational flowthrough the filter and is limited to a slow flowrate. Slow sand filters are generally very largestructures installed in large aquatic systems.

The rapid sand filter forces water throughthe sand under pressure and has a greater flowrate and, therefore, a larger capacity per sizethan the slow sand filter. Commercially man-ufactured rapid sand filters are generally toolarge to be used in a small enclosure contain-ing below 750 litres of water. For largerenclosures, small swimming pools or hottubs, rapid sand filters are available commer-cially. There are also small to very large-sizeunits developed specifically for the aquacul-ture industry (see Plate 2).

With all mechanical filters, suspended par-ticles are merely concentrated but not re-moved from the system. These filters mustbe cleaned regularly to remove the physicalparticulates or the organic components willdecompose and chemically corrupt the waterquality.

Filters that can remove dissolved sub-stances from water are considered chemicalfilters. A common type of chemical filter thatis currently in many household is the waterpurifier for drinking water. These filterscontain cartridges with mechanical prefiltersand activated carbon chemical filters. Larger

versions of these activated carbon filters havebeen in use for many years to assist inmaintaining water quality in aquariums.

Activated carbon has unique propertiesthat make it an ideal material for amphibianenclosure chemical filtration. It is a highlyadsorptive and porous material that readilyremoves dissolved organic compounds, mi-cro-particulate and certain reactive non-ionicchemicals (e.g. free chlorine). It will evenremove some ions, such as copper (Periasamy& Namasivayam, 1996; Seco et al., 1999),although it is not as effective as other means.The numerous pores create an effective sur-face area exceeding 10 000m2 kg� 1 of car-bon (Kinne, 1976). As water passes throughthis porous matrix of activated carbon, organ-ic compounds loosely bond with the carbonand are effectively eliminated from the water.The porous matrix catches very small micro-particulate (e.g. some bacteria), thus acting asa fine mechanical filter, which can reduce itscapacity as a chemical filter if flow is inhib-ited. Activated carbon filters should alwayshave a mechanical prefilter to remove most ofthe particulate before the chemical and finemechanical filtration by the carbon filter.

It is important to remember that chemicalfilter media have a finite capacity to absorbtoxins and chemicals. The chemical mediawill ultimately become saturated with toxinsand, if they are not changed regularly, theywill begin releasing those toxins back into thewater. Most chemical filters give no visiblesigns of when this occurs. It is generallyrecommended that chemical media be chan-ged every 2–4weeks but this will vary widelydepending on the amount of media in thefilter and the chemical load in the water. Werecommend the use of chemical filtration innew systems or in systems with a knownproblem that the chemical medium will ad-dress.

The last type of filter is the biological filter.It is perhaps the most important and the mostcomplex type of filtration in any system. Itsaction is neither mechanical nor chemical. Itsfunction is the accumulative effects of acommunity of millions of living bacteria.Once this community is established in an

Plate 2. A simple rapid sand filter designed for whirl-pool baths and small swimming pools is excellent forfiltering larger volumes of water. These are readilyavailable from many sources. R. A. Odum, ToledoZoological Society.



enclosure, its actions appear unified, as if thecommunity was in itself a single separateorganism. A biological filter possesses manybasic characteristics of life itself and, for thepurpose of this discussion, should be consid-ered both as a community of organisms(Hovanec et al., 1998; Burrell et al., 2001)and as a separate life form that lives insymbiosis with the animals housed in theenclosure.

Biological filters remove the toxic nitro-genous metabolic waste products of the ani-mals and other organisms (e.g. decomposingbacteria) from the water in an enclosure. Mosttotally aquatic vertebrates excrete ammoniaas a metabolic waste product. The primaryfunction of a biological filter is to oxidizetoxic ammonia/ammonium (NH3/NH4

1) intoa less toxic form, ultimately producing thenitrate ion (NO3

� ). It should be noted that freeammonia (NH3) is the most toxic form ofammonia/ammonium. The form of ammoniapresent depends on temperature and pH (seeTable 2).

This process of bacterial oxidation of am-monia is called nitrifying. It is not the inten-tion here to discuss the details of thebiological processes that occur in biologicalfiltration. Below is a basic equation of theoverall nitrifying process (Lees, 1952):

Circulation through a biofilter is normallyaccomplished using pumps and airlifts. Watermust flow through the filter at a medium-slowrate in order for the bacteria to be able toadsorb the nitrogenous wastes (Hawkins &Anthony, 1981; Wickins & Helm, 1981). Theminimum flow rate is determined as the slow-est flow rate that maintains aerobic conditionsthroughout the entire biofilter medium. If theflow rate is too slow or ceases entirely, thefilter will become anaerobic and will startproducing ammonia rather than adsorbing it(Stickney, 1979). If this occurs, the nitrifyingbacteria will quickly die and be replaced byspecies that favour living in an oxygen-defi-cient environment. Many species of anaero-

bic bacteria produce toxic by-products, bothinorganic (e.g. hydrogen sulphide) and or-ganic (e.g. Clostridium), which could resultin a build-up of toxins that could kill theanimals that are maintained in the enclosure.

Common types of biofilters that have beenused for many years include the under-gravelfilter, the reverse-flow under-gravel filter,trickle filters and sponge filters. All thesehave demonstrated their effectiveness andinformation on their function and setup isreadily available.

One of the newer advances in biofilters isthe fluidized bed filter. These compact filtersutilize the same basic technology as an under-

gravel filter with several major improve-ments. A fluidized bed filter is usually in theform of a clear plastic column 2 � 5–12 � 5 cmin diameter and 0 � 3–1 � 0m long, whichusually hangs on the outside of the tank. Asmall pump, with a mechanical prefilter toremove particulates, injects water to the bot-tom of the column. The water flows upwardsthrough the column and overflows back intothe enclosure. The flow of water is just greatenough to keep the sand suspended in thewater column (fluidized) without forcing itout of the filter. This sand provides a hugesurface area for bacterial growth, and becauseit is constantly suspended in the water, theentire medium is aerobic and provides an

NO2–1

NitriteNO3

–1

NitrateNH3/NH4

+1

Ammonia/Ammonium

1C

PH

MORE ACIDIC MORE BASIC

6 � 0 6 � 5 7 � 0 7 � 5 8 � 0 8 � 5 9 � 0 9 � 5 10

5 0 � 013 0 � 040 0 � 12 0 � 39 1 � 2 3 � 8 11 28 5610 0 � 019 0 � 059 0 � 19 0 � 59 1 � 8 5 � 6 16 37 6515 0 � 027 0 � 087 0 � 27 0 � 86 2 � 7 8 21 46 7320 0 � 040 0 � 13 0 � 40 1 � 2 3 � 8 11 28 56 8025 0 � 057 0 � 18 0 � 57 1 � 8 5 � 4 15 36 64 8530 0 � 080 0 � 25 0 � 80 2 � 5 7 � 5 20 45 72 89

Table 2. Percentage un-ionized (i.e. more toxic) am-monia in aqueous ammonia solutions as a function ofpH and temperature (Florida Department of Envir-onmental Protection, 2001).



excellent base for nitrifying bacteria. Thesefilters are rapidly gaining in popularity andreplacing the more conventional wet/drytrickle filters. One of the authors has usedQuicksands fluidized bed filters for yearswith excellent results. However, fluidizedbeds deteriorate rapidly when water ceasesto flow through them (e.g. during a powerfailure).

Establishing a new biofilter is almost anurturing process that can take several weeksto several months. The filter must be fedammonia and monitored through the process.When fully established, a properly sized filteris capable of oxidizing the ammonia load tonitrates quickly, and there are no ammonia ornitrites detectable in the system. Feeding thefilter can be accomplished by using natural(animals) or artificial (dilute ammonia or anammonium salt) sources of ammonia.

Nitrifying bacteria will also invade a me-chanical filter and function as a biofilter if theflow rate is not too rapid. Certain types ofmechanical filters provide the appropriateconditions for biofiltration better than others.One of the best is the slow sand filter.

Maintaining a biofilter

Again, the biofilter should be thought of as aliving entity in an enclosure. The bacteriamust be supplied with a constant flow ofoxygenated water at the appropriate tempera-ture, which contains low levels of ammoniaand nitrite as food. Without these necessities,the filter will suffocate and starve. If the tankmust sit idle (without animals), move thebiofilter to a tank with animals to keep itgoing, or simply feed it ammonia every day.Also, attention must be paid to the amount oftime a biofilter is shut down during servicing.The longer it is down, the more bacteriasuffocate and the less effective the filter willbe until it recovers. Do not clean a biofilterexcessively; just rinse the media if and whennecessary. Never use chemical disinfectantson a biofilter unless you plan start the initi-alization process again. Antibiotics can alsokill a biofilter, so always treat sick animals ina separate ‘hospital’ tank if possible.

It is a good idea to always keep a few extrabiofilters going in tanks with heavy simulatedbioloads (see Plate 3). The filters can beattached to a disinfected tank and liquidhousehold ammonium (with no detergent orperfume), added daily at a rate of four to fivedrops per c. 38 litres of water. The water mustbe daily monitored for ammonia, and theamount of household ammonia added can beadjusted as appropriate. In this way, when anew tank is set up, an established biofilter isavailable without having to wait for a new oneto cycle. This filter should be free of potentialpathogens because it has not been in contactwith a system that contained animals. This isvital for that unexpected batch of larvae. Also,if appropriate precautions are taken, thesefilters could be used in a biosecure situation.

Plants

Another often-overlooked form of filtration(bio and chemical) comes with the addition ofliving plants to the system. Plants help toremove organic as well as inorganic wastefrom the water and are a great source ofoxygen. Some aquarists use only living plants

Plate 3. A biofilter cycling tank. Different types ofbiofilters, including trickle, sponge and fluidized bedfilters, are cycled in this tank using an artificial sourceof wastes (ammonia). These filters can then be trans-ferred to other tanks containing animals, withoutcause for concern about transferring pathogensbetween groups. Note the instructions to the keeperfor daily maintenance on the left side of the tank. R. A.Odum, Toledo Zoological Society.



for filtration. Plant-based filter systems areso effective that they can even be used fortreating human sewerage (Levy, 2007).Furthermore, plants greatly enhance the attrac-tiveness of an aquarium and provide oviposi-tion sites for many amphibians. If theinhabitants of the tank are large or active andtend to tear up rooted plants, it is possible toculture plants in a separate tank adjacent to theanimal tank, and use filters to pump water fromone tank to the other. Just letting the tendrilsof a potted plant, like Pothos Epipremnumaureum, dangle into a tank can significantlyreduce nitrogenous wastes, especially nitrates.

Water testing

Water testing kits and devices are readilyavailable from many sources. They vary fromsimple colorimetric systems (e.g. dip sticks,cells) to highly sophisticated and accuratespectrophotometers (i.e. like those manufac-tured by Hach). In most cases, the simplecolorimetric systems are adequate for theamphibian keeper to monitor water qualityand diagnose problems. When a system isinitialized, the water should be tested fre-quently. Once established, it can be moni-tored less frequently. Ammonia/ammonium,nitrites, nitrates, pH, hardness and phosphatesare tests that should be performed, at leastinitially. It is highly recommended that theprimary water supply be monitored occasion-ally. Municipal water supplies frequentlychange their chemical composition depend-ing on the situation of their supply or formaintenance (i.e. water-line repairs usuallyare followed by higher concentrations ofchlorine to disinfect the lines).

Without water testing, the amphibian kee-per cannot know the quality of the water theyare providing for their animals, making themoblivious to this most important aspect ofamphibian husbandry. Many of the signifi-cant and commonly encountered toxins inaquatic systems are in such low concentra-tions they cannot be seen nor do they have asmell. Testing is a better strategy than merefaith that the water is ‘good’.

Water changes

Regular water changes are essential to rid asystem of the minor toxins that are notmanaged (like nitrates and phosphates), andto replenish any nutrients that were absorbedby the plants and animals. A minimum of10–20% water change every 1–2weeks willgenerally suffice.

Waste-water management

With the realization that diseases spread byhuman activity have caused declines, and insome cases outright extinction of amphibianpopulations, considerable attention should begiven to how waste water from amphibianfacilities is disposed of (see also Robertsonet al., in press).

CONCLUSION

Understanding water quality is essential forthe long-term successful breeding, rearingand maintaining of amphibians in captivity.Proper monitoring of water can establishnegative trends in aquatic systems beforeproblems arise. It is often the case that thedamage is done before an increase in mortal-ity and morbidity is observed.

When a problem is encountered, the waterquality should be tested (along with otherpossibilities) to determine if there is a cause-and-effect relationship. If eggs or larvae die,water quality should be one of the first areasexamined to find a possible cause. If mortal-ity in adult amphibians is a problem, checkthe quality of the water supply. If a relation-ship between water quality and mortality orhealth problems is discovered, improve thequality of the aquatic environment. The solu-tions to water quality problems are many andanswers are only found by applying theprinciples of water management.

Checklist for a healthy aquatic system

� Start with high-quality water.� Filter the water three different ways: me-

chanically, chemically and biologically.



� Clean mechanical media at least weekly,replace chemical media regularly and treatbiological media as living organisms.

� Do not overcrowd a tank: keep the bioloadreasonable.

� Do not overfeed the animals: uneaten foodand excessive faeces will foul the water.

� Test the quality of the water regularly (atleast ammonia and pH levels). Ask your-self, ‘Would I drink this water?’.

� Where possible, incorporate live plants.� Perform water changes often.� Monitor water quality (not discussed in

this paper).

PRODUCTS MENTIONED IN THETEXT

Hach: integrated water-analysis system spec-trophotometer, manufactured by Hach Com-pany, Loveland, CO 80539, USA. http://www.hach.comHomegrown Six Pack: trace-element mix,manufactured by Homegrown Hydroponics,http://www.homegrown-hydroponics.com/Prime: aquatic conditioner to removechlorine, chloramine and ammonia, manufac-tured by Seachem Laboratories Inc., Madi-son, GA 30650, USA. http://www.seachem.comQuicksands: fluidized bed filter, manufac-tured by Bio-Con Labs Inc., Gainsville, FL,USA. http://www.bioconlabs.com

REFERENCESARTHUR, J. W. & EATON, J. G. (1971): Chloramine toxicityto the amhipod, Gammarus pseudolimnaeus, and thefathead minnow, Pimephales promelas. Journal of theFisheries Research Board of Canada 28: 1841–1845.BALL, I. R. (1967): The relative susceptibilities of somespecies of fresh-water fish to poisons. I. Ammonia.WaterResearch 1: 767–775.BRUNGS, W. A. (1971): Chronic effects of low dissolvedoxygen concentrations on fathead minnow (Pimephalespromelas). Journal of the Fisheries Research Board ofCanada 31: 1119–1123.BURRELL, P. C., PHALEN, C. M. & HOVANEC, T. A. (2001):Identification of bacteria responsible for ammonia oxida-tion in freshwater aquaria. Applied and EnvironmentalMicrobiology December: 5791–5800.CARLSON, A. R. & SIEFERT, R. E. (1974): Effects ofreduced oxygen on the embryos and larvae of lake trout(Salvelinus namaycush) and largemouth bass (Micro-

Micropterus salmoides). Journal of the Fisheries Re-search Board of Canada 31: 1393–1396.CULLEY, D. D. (1992): Managing a bullfrog researchcolony. In The care and use of amphibians, reptiles, andfish in research: 30–40. Schaeffer, D. O., Kleinow, K. M.& Krulisch, L. (Eds). Bethesda, MD: Science Center forAnimal Welfare.CUMMINS, C. P. (1989): Interaction between the effects ofpH and density on growth and development in Ranatemporaria L. tadpoles. Functional Ecology 3: 45–52.DUELLMAN, W. E. & TRUEB, L. (1986): Biology of amphi-bians. Baltimore, MD: Johns Hopkins University Press.ENVIRONMENTAL PROTECTION AGENCY (1976): Quality cri-teria for water, July 1976. Washington, DC: U.S. Envir-onmental Protection Agency.FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION(2001): Calculation of un-ionized ammonia in freshwater: Storet Parameter Code 00619. Tallahassee, FL:Florida Department of Environmental Protection. ftp://ftp.dep.state.fl.us/publabs/assessment/guidance/unnh3sop.docGULIDOV, M. V. (1969): Embryonic development ofthe pike (Esox lucius L.) when incubated under dif-ferent oxygen conditions. Problems of Ichthyology 9:841–851.HAWKINS, A. D. & ANTHONY, P. D. (1981): Aquariumdesign. In Aquarium systems: 1–46. Hawkins, A. D.(Ed.). New York, NY: Academic Press.HERBERT, D. W. M. & SHURBEN, D. S. (1965): Thesusceptibility of salmonid fish to poisons under estuarineconditions. II. Ammonium chloride. International Jour-nal of Air and Water Pollution 9: 89–91.HOVANEC, T. A., TAYLOR, L. T., BLAKIS, A. & DELONG, E. F.(1998): Nitrospira-like bacteria associated with nitriteoxidation in freshwater aquaria. Applied and Environ-mental Microbiology 64(1): 258–264.ISIS (2007): ISIS species holdings. Minneapolis, MN:International Species Information Systems. http://app.isis.org/abstracts/abs.aspJOFRE, M. B. & KARASOV, W. H. (1999): Direct effect ofammonia on three species of North American anuranamphibians. Environmental Toxicology and Chemistry18(8): 1806–1812.KINNE, O. (1976): Cultivation of marine organisms: waterquality management and technology. In Marine ecology3(1): 19–300. Kinne, O. (Ed.). London: Wiley.KLINGLER, K. (1957): Sodium nitrate, a slow acting fishpoison. Schweizerische Zeitschrift fuer Hydrologie 19(2):565–578.LEES, H. (1952): The biochemistry of the nitrifyingorganisms. 1. The ammonia-oxidizing system of Nitro-somonas. Biochemical Journal 52: 134–139.LEVY, S. (2007): From effluence to affluence. AudubonMagazine March-April. http://audubonmagazine.org/solutions/solutions0703.htmlMARCO, A., QUICHANO, C. & BLAUSTEIN, A. R. (1999):Sensitivity to nitrate and nitrite in pond-breeding amphi-bians from the Pacific Northwest, USA. EnvironmentalToxicology and Chemistry 18: 2836–2839.ODUM, R. A., MCCLAIN, J. M. & SHELY, T. C. (1984):Hormonally induced breeding and rearing of white’s



treefrog, Litoria caerula (Anura: Pelodryadidae). InProceedings 7th reptile symposium on captive propa-gation husbandry, July 26–29, 1983, Dallas, Texas:42–52. Tolson, P. J. (Ed.). Thurmont, MD: ZoologicalConsortium.PAVAJEAU, L., ZIPPEL, K. C., GIBSON, R. & JOHNSON, K. (Inpress): Amphibian Ark and the 2008 Year of the FrogCampaign. International Zoo Yearbook 42.DOI:10.1111/j.1748-1090.2007.00038.x.PERIASAMY, K. & NAMASIVAYAM, C. (1996): Removal ofcopper(II) by adsorption onto peanut hull carbon fromwater and copper plating industry wastewater. Chemo-sphere 32(4): 769–789.PRITCHARD-LANDE, S. P. & GUTTMAN, S. L. (1973): Theeffects of copper sulfate on the growth and mortality rateof Rana pipiens tadpoles. Herpetologica 29(1): 22–27.ROBERTSON, H., EDEN, P., GAIKHORST, G., MATSON, P.,SLATTERY, T. & VITALI, S. (In press): An automaticwaste-water disinfection system for an amphibian cap-tive-breeding and research facility. International ZooYearbook 42. DOI:10.1111/j.1748-1090.2008.00048.x.ROUSE, J. D., BISHOP, C. A. & STRUGER, J. (1999): Nitrogenpollution: an assessment of it threats to amphibian survi-val. Environmental Health Perspectives 107: 799–803.RUSSO, R. C., SMITH, C. E. & THURSTON, R. V. (1974):Acute toxicity of nitrite to rainbow trout (Salmo gaird-nieri). Journal of the Fisheries Research Board ofCanada 31: 1653–1655.SCHMUCK, R., GEISE, W. & LINSENMAIR, K. E. (1994): Lifecycle strategies and physiological adjustment of reedfrogtadpoles (Amphibia, Anura, Hyperoliidae) in relation toenvironmental conditions. Copeia 4: 996–1007.SECO, A., GABALDON, C., MARZAL, P. & AUCEJO, A. (1999):Effect of pH, cation concentration and sorbent concentra-tion on cadmium and copper removal by a granularactivated carbon. Journal of Chemical Technology andBiotechnology 74: 911–918.

SIEFERT, R. E. & SPOOR, W. A. (1974): Effects of reducedoxygen on embryos and larvae of white sucker, cohosalmon, brook trout and walleye. In The early life historyof fish. The proceedings of an international symposium.Oban, Scotland, May 17–23, 1973: 487–495. Blaxter,J. H. S. (Ed.). Berlin: Springer-Verlag.SIEFERT, R. E., CARLSON, A. R. & HERMAN, L. J. (1975):Effects of reduced oxygen concentrations on the early lifestages of mountain whitefish, smallmouth bass, and whitebass. Progressive Fish-Culturist 36: 186–190.SMITH, J. M. D. (1982): Introduction to fish physiology.Neptune, NJ: TFH Publications.STICKNEY, R. S. (1979): Principles of warmwater aqua-culture. New York, NY: John Wiley and Sons.TABATA, K. (1962): Toxicity of ammonia to aquaticanimals with reference to the effect of pH and carbondioxide. Bulletin of the Tokai Regional Fisheries Re-search Laboratory 34: 67–74.WARNER, S. C., DUNSON, W. A. & TRAVIS, J. (1991):Interaction of pH, density, and priority effects on thesurvivorship and growth of two species of hylid tadpoles.Oecologia 88: 331–339.WESTIN, D. T. (1974): Nitrate and nitrite toxicityto salmonid fishes. Progressive Fish-Culturist 36:86–89.WHITAKER, B. R. (2001): Water quality. In Amphibianmedicine and captive husbandry; 147–157. Wright, K.M. & Whitaker, B. R. (Eds). Malabar, FL: KriegerPublishing.WICKINS, J. F. & HELM, M. M. (1981): Sea watertreatment. In Aquarium systems: 63–128. Hawkins,A. D. (Ed.). New York, NY: Academic Press.

Manuscript submitted 27 July 2007; revised 3February 2008; accepted 5 February 2008



Amphibian water quality: approaches to an essential ......2019/02/23 · effective at removing...

Documents

Transcript of Amphibian water quality: approaches to an essential ......2019/02/23 · effective at removing...