Amphibian water quality: approaches to an essential environmental parameter - Amphibian Ark
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40 AMPHIBIAN CONSERVATION
Int. Zoo Yb. (2008) 42: 40–52
DOI:10.1111/j.1748-1090.2008.00053.x
Amphibian water quality: approaches to an
essential environmental parameter
R. A. ODUM1 & K. C. ZIPPEL2
1
Toledo Zoological Society, Toledo, Ohio 43614, USA, and 2Amphibian Ark/CBSG,
Apple Valley, Minnesota 55124, USA
E-mail: RAOdum@aol.com
Appropriate water quality is essential for maintaining and Dendrobatidae are the most common captive-
breeding amphibians in captivity. Aquatic systems that bred anurans in zoos (ISIS, 2007).
maintain water quality have been employed for many
years in the aquaculture and aquarium industries. These There are critical differences between
techniques are now more commonly being utilized for the husbandry of amphibians, which have
amphibians. Using information from the work of the the most diverse reproductive strategies, and
authors and published literature on amphibians and fish, the other tetrapod vertebrates (reptiles, mam-
benchmarks are provided for common water-quality
parameters for amphibians.
mals) (Duellman & Trueb, 1986). Their skins
are highly permeable, making them prone to
Key-words: amphibian; benchmark; breeding; water- desiccation and absorption of environmental
quality parameters. pollutants directly through their skin. Perhaps
the most descriptive metaphor that best de-
scribes the amphibians is, ‘Think of these
INTRODUCTION
animals as fish with legs’. Fish are managed
Long relegated to a footnote in many reptile in captivity by providing them with a clean
facilities, it is only recently that amphibians and appropriate water environment; this is
have been receiving the attention they de- exactly the same way in which amphibians
serve from zoos and aquariums. Unfortu- should be managed.
nately, this attention was slow in coming and Any supply of water for amphibians must
was only in response to the urgency of the meet certain minimal requirements to main-
current extinction crisis facing the entire tain the health and normal physiology of the
class. In reaction to the crisis, the zoo com- animals (Schmuck et al., 1994). Water from
munity, IUCN – The World Conservation either a natural source or a treated source (e.g.
Union and other conservation organizations municipal water supply) is not a pure sub-
have inaugurated a response to create captive stance, but a suspension and solution of
survival-assurance populations to preserve various organic and inorganic components.
threatened species and to allow the option of These additional substances in the water
future reintroductions, if necessary (Pavajeau might be required to maintain the organism,
et al., in press). might have no effect or might be detrimental.
Regrettably, it has quickly become appar- Amphibians have invaded many different
ent that there are many more taxa in need of niches, and the individual water requirements
help than there are facilities capable of pro- for a given species and its tolerance to
viding assistance. Although zoos have had a specific toxins vary. It should be noted that
great deal of experience with the amniotic different life stages of an amphibian may also
terrestrial vertebrates, few have had a long have different requirements. The overall con-
history with amphibians. Most taxa have centrations of these substances and sus-
never been maintained in captivity and, of pended material in a supply of water are
those that have, most have not been bred. conveniently grouped together under the term
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London
WATER QUALITY AND AMPHIBIAN CONSERVATION 41
‘water quality’. This includes all aspects of in evaluating a water supply is to perform
the water (e.g. pH, inorganic salts, organic appropriate tests for dissolved substances, pH
compounds, metabolic waste products, dis- and hardness. At least initially, it is very
solved gases and bacterial suspensions). useful to have your water source tested by a
This article is a brief overview of water laboratory qualified for this purpose. Most
quality as it relates to amphibian husbandry. US counties or states provide water-testing
Most of the techniques presented have been services for water supplies intended for hu-
developed by the aquarium and aquaculture man consumption, and there are also many
communities to maintain and reproduce fish commercial laboratories that provide these
(Stickney, 1979). These have been success- services at a reasonable cost. The results of
fully adapted by some institutions to maintain these tests will help to identify any pretreat-
and breed amphibians. The key to these ment that is necessary for the water before it
successes is in part owing to an appreciation can be utilized for amphibians. The human
and knowledge of water quality and the potable water standards (less disinfectants)
systems necessary to maintain high-quality are a good start for evaluating water supply.
water (as well as an understanding of the If you would not drink it, then it is probably
biology of the animals we maintain). Clearly, not the best water for your animals.
water quality is far more important for those Many amphibian facilities use a local mu-
animals that spend most or all of their time in nicipal water source for their operations, but
it (e.g. larvae larviforms and other aquatic some preconditioning of the water is almost
adults), but even for those who might only always necessary. Municipal water is usually
rely on terrestrial substrate moisture, water disinfected with free chlorine (Cl2) or chlor-
quality is an essential factor for health of the amines. Eliminating these disinfectants is a
animal. first step in pretreating water. If free chlorine
is the disinfectant, simply ageing and aerating
PARAMETERS FOR WATER QUALITY tap water for 24 hours is all that is required to
condition it for use with amphibians. Aera-
Extensive work has been carried out in the
tion will also drive off other harmful gases
field of aquaculture to quantify the relation-
(carbon dioxide, nitrogen, hydrogen sul-
ship between water quality and the health of
phide) and bring desired gases (oxygen) into
fish and some aquatic invertebrates (Envir-
equilibrium between the water and the atmo-
onmental Protection Agency, 1976). In con-
sphere.
trast, the published literature for amphibians
If chloramines are used as a disinfectant in
is relativity scant.
the water supply, this ageing process is in-
Table 1 shows some common parameters
effective. The chloramines need to be re-
for the water quality for amphibians. These
moved through chemical filtration or through
parameters were developed from the pub-
chemical treatment. Activated carbon is less
lished literature for amphibians and fish, as
effective at removing chloramines than free
well as the direct experience of the authors.
chlorine from water. There are commercially
These are only guidelines. The tolerance to
available filters specifically designed to re-
common toxins and the requirements for each
move chloramines that contain carbon and
species are still unknown for the majority of
additional media. To remove chlorine chemi-
amphibian taxa. Therefore, these suggested
cally, create a saturated solution of sodium
levels should be considered only for guidance
thiosulphate (Na2S2O3) in water by adding it
in evaluating system performance.
to a small volume of water until no more
chemical will dissolve (note that Na2S2O3
Water sources
is usually available as a pentahydrate
Water is available from many sources for Na2S2O3 5H2O, which is suitable for this
amphibian husbandry, and water quality of application). This solution can then be used
these sources varies extensively. A first step to dechlorinate water by adding one drop of
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London42
WATER QUALITY METHODS OF
PARAMETER EFFECT ON AMPHIBIANS ACCEPTABLE LEVELS ALLEVIATION COMMENTS REFERENCES
1
Water hardness Hard water can cause skin o75 mg litre (ppm) of Diluting hard water Whitaker (2001)
(dissolved Ca problems in some species CaCO3 for animals that with RO, DI or
and Mg salts) by disrupting normal require soft water distilled water
osmotic regulation of the 4100 mg litre 1 should Hardening soft
amphibian. Most show a be considered hard water water with Ca and
preference for ‘soft water’ for an amphibian Mg salts (only
but this can be species recommended for
dependant reconstituting RO,
DI distilled water)
Dissolved oxygen as Oxygen is needed for 480% Saturation Aeration Some anurans and Gulidov (1969);
O2 amphibian respiration salamanders may be Brungs (1971);
and aerobic processes. able to tolerate very Carlson & Siefert (1974);
low levels of oxygen Siefert & Spoor (1974);
Siefert et al. (1975);
Odum et al. (1984);
Whitaker (2001)
Gas supersaturation Gas bubble disease Gases should be at Aeration until Common in well water and
equilibrium with equilibrium is pressurized municipal
atmosphere achieved water sources, especially
when cold
Ammonia/ Very toxic o0 2 mg litre 1, Biological filtration, Metabolic waste product Tabata (1962);
Ammonium – N as unionized chemical filtration Ammonia/ammonium Herbert & Shurben (1965);
NH3/NH14 ammonia with appropriate ratio is pH and Ball (1967);
medium, or water temperature dependant Jofre & Karasov (1999);
changes (see Table 2) Rouse et al. (1999);
Whitaker (2001)
Nitrites NO2 Toxic o1 0 mg litre 1, Biological filtration, A product of aerobic Klingler (1957);
but ideally zero chemical filtration biological action on Russo et al. (1974);
with appropriate ammonia NH3/NH1 4 Westin (1974);
medium or water Marco et al. (1999);
changes Whitaker (2001)
1
Nitrates NO3 Slightly toxic o50 0 mg litre Remove by This is the end product of Westin (1974);
photosynthetic biological filtration Whitaker (2001)
action of green
plants and by
water changes
AMPHIBIAN CONSERVATION
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of LondonPH Can cause metabolic Species dependant, but Change water source Cummins (1989);
problems if not within usually near neutral. or add appropriate Warner et al. (1991);
acceptable range for pH below 6 and above buffers Whitaker (2001)
species, disrupts ion 8 are potentially a problem
exchange
Chlorine Cl2 Very toxic 0 Aerate for 24 hours Some adult forms seem to be Arthur & Eaton (1971);
or add chemical able to tolerate chlorinated Culley (1992);
dechlorinator water: Ceratophrys R.A. Odum, pers. obs
(e.g. sodium ornata, Rana catesbeiana,
thoisulphate) Ambystoma texanum,
Ambystoma tigrinum,
Litoria caerulea,
Ichthyophis kohtaoensis
1
Chloramines Very toxic o0 01 mg litre as Cl Use chemical Similar to Cl2 in toxicity, but Environmental Protection
(ClNH2, ClN2H, treatment specific also releases ammonia Agency (1976)
WATER QUALITY AND AMPHIBIAN CONSERVATION
ClN3) for chloramines
(e.g. Prime)
1
Copper (Cu) Toxic o0 05 mg litre Carbon filtering and Copper water supply pipes Pritchard-Landé & Guttman
carbonate can be flushed before (1973)
precipitation collecting water
Do not use copper
pipes
Phosphates (PO34 ) Toxic to many animals, Toxicity may be species Phosphate sponges Atelopus spp adults seem
interferes with calcium specific. EPA limits and filters are to be particularly sensitive
1
metabolism PO34 to 10 mg litre . available to absorb to phosphate toxicity
Applications of phosphates
1 mg litre 1 are
considered effective
for preventing pipe
corrosion
Table 1. Water-quality parameters for maintenance of amphibians in captivity: DI, de-ionized; DO, dissolved oxygen; EPA, Environmental Protection Agency;
RO, reverse osmosis.
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London
4344 AMPHIBIAN CONSERVATION
the saturated thiosulphate solution for every field where it might have picked up fertilizers,
4 litres of water. Care must be taken not to use herbicides or insecticides? Another thing to
too much sodium thiosulphate (beyond the consider is that this water might be contami-
saturated solution dose as described here) nated with diseases or parasites from wild
because it can be toxic. Also, the chemical animals. If the source is in an area where
reaction between thiosulphate and chlora- chytrid fungus Batrachochytrium dendroba-
mines leaves free ammonia in the water, tidis is present, the water source should be
which is a significant toxin that needs to be screened for its presence. Alternatively, the
removed (Smith, 1982). ‘stuff’ living in the water could be beneficial
Another common source used in facilities for the care of the animals, particularly small
is well water. Well water can be an accepta- larvae. Natural pools teeming with inverte-
ble, consistent source of water for use with brate life offer more diversity and nutrition
amphibians but again one must test for pH, than could ever be cultured artificially. One of
hardness, metal content and, in coastal areas, the authors (R.A.O.) was successful only
salinity. In some regions, especially where after multiple attempts to rear filter-feeding
water is pumped up from limestone bedrock, Banded rubber frog Phrynomantis bifasciatus
well water can be too hard and the pH too larvae by using pond water containing large
high – test and treat accordingly. In agricul- amounts of green algae and protozoa. Of
tural areas, well water can also be high in course, an unfiltered natural water source is
phosphates (PO4 3) and nitrates (NO3 1) not appropriate for biosecure situations. Such
from fertilizers that seep into the aquifer. sources would have to be filtered and disin-
These substances cause algal blooms, and at fected to assure that no pathogens are intro-
higher concentrations are toxic to animals. duced into a biosecure colony of amphibians.
Well water can also be supersaturated with If tap water is not acceptable and a reliable
nitrogen and carbon dioxide, devoid of oxy- outdoor supply is unavailable, bottled water
gen and can even contain lethal quantities of might be an acceptable alternative. Again, the
hydrogen sulphide. Vigorously aerating the pH and hardness, and even the chlorine level,
water for at least a day before use will drive must be tested. Bottled spring water pumped
off the nitrogen, carbon dioxide and hydro- up through bedrock can be unacceptably hard
gen sulphide, as well as raise the oxygen and basic. Furthermore, purity-testing re-
content. Aeration can also help precipitate quirements for bottled water are not as strict
some compounds (i.e. iron) before the water as for tap water. A recent survey by the
enters the animal enclosure. Natural Resources Defense Council (NRDC)
Rainwater has also been used for captive showed that one in three samples of bottled
amphibians. This resource can be a solution water contained contaminants, including syn-
in isolated facilities that do not have other thetic organic chemicals, coliform bacteria or
water supplies available. Rain water is natu- even arsenic. In some cases, bottled ‘spring’
rally soft, perhaps too soft for some species water was shown to be simply filtered bottled
(see reconstituting water below). Test for pH tap water. Consult the NRDC website or
if air pollution is a consideration (acid rain). write/call NRDC Headquarters, 40 West
Also, one must consider how the rain is 20th Street, New York, NY 10011, USA
collected. Do not collect rain from a galva- (Tel:11-212-727-2700), to get the results for
nized steel roof or one that has otherwise a particular bottled water source.
been treated chemically. If the water supply in a facility has high
Water that collects in natural basins, such levels of copper or other contaminants that
as ponds, streams and lakes, can be a good cannot be addressed by other means, reverse
source of acceptable water. One must check osmosis (RO) water should be considered as a
where the water is coming from; for example, possible solution. This can be a safe and
is it draining from a large parking area consistent way to ensure a constant supply of
covered with oil spills, or from a farmer’s very pure water, which in itself creates other
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of LondonWATER QUALITY AND AMPHIBIAN CONSERVATION 45 problems. Like rain water and distilled water, Designing water systems for amphibians RO water is essentially pure. In fact RO water is, in many cases, too pure to be used as it is. Two general types of aquatic system are It may be used for species that normally live currently used to house amphibians in collec- in pure rain water, such as some dendrobatids tions – the open system and the semi-closed and other phytotelm (water accumulated in system. The open system allows fresh, clean tree holes and plants such as bromeliads) water to enter the enclosure, at a flow rate dwellers. For many other species, chemicals whereby the water remains within the enclo- (salts for osmotic issues and trace elements sure for a short period of time and is then for health considerations) need to be added. discharged. This flow may be established by a Common symptoms of osmotic imbalance variety of methods, including misting, spray- created by too pure water include bloating ing and direct influx of liquid water. It may be and kidney dysfunction. continuous or intermittently added (i.e. Commercial additives containing the re- timer). In semi-closed systems, a quantity of quisite trace elements are available. A simple water is added and removed periodically (e.g. preparation to reconstitute RO water is listed weekly or monthly) as a percentage of the below. This mix was developed largely by total water volume in the system. fish and aquatic plant hobbyists, and fine- The open system is one in which water and tuned for amphibians. other matter, food and energy, are continually In 100 litres of RO water dissolve: entering (influent) and leaving (effluent) the 4 0 g calcium chloride CaCl2 enclosure. Waste products, organic toxins, 4 6 g magnesium sulphate MgSO4 7H2O decaying organic matter, dead food items, 3 6 g potassium bicarbonate KHCO3 inorganic compounds, etc, are flushed from 3 0 g sodium bicarbonate NaHCO3 the enclosure, and the water quality is main- 0 13 g commercial trace-element mix tained as long as the rate of influent flow is Dissolving the crystals in a jar of water first sufficient. No type of enclosure filtration is and then adding the solution to the storage needed because the water is never in the tank will ensure proper mixing. The final enclosure very long. In theory, open systems composition is similar to moderately soft can be the least complicated, most mainte- fresh river water, with roughly 31 general nance-free type of system. Another benefit to hardness and 21 carbonate hardness, ideal these systems is that potentially pathogenic Ca:Mg (3:1) and Na:(Ca1Mg1K) (1:4) ra- organisms do not build up within the enclo- tios, and depending on aeration levels, a pH sure because they are continually removed around 7 4. The trace-element mix provides with the effluent. The main problem with small quantities of elements that are usually such a system is having a continuous suffi- present in low concentrations in most bodies cient supply of appropriate quality (and tem- of water. Trace-element mixes are available perature) water. Open systems are commonly through hydroponics suppliers (e.g. Home- employed in large aquaculture operations, grown Six Pack, Homegrown Hydroponics). such as fish hatcheries, where large quantities RO filters do not remove everything. Some of water are pretreated before they are used. nitrates, phosphates and silicates, which can The most common type of aquatic system be present in tap water at low concentrations, used by the aquarist to maintain water quality can pass through. Although not toxic at low is the semi-closed system. What has been levels, these substances can cause unsightly learned in the aquarium field has been suc- algal blooms. A de-ionizing (DI) filter car- cessfully adapted for use within amphibian tridge used in conjunction with the RO filter enclosures at many institutions. Incorporating will help eliminate nitrates and phosphates, mechanical, chemical and biological filtration should they prove problematic. A DI filter with the occasional partial water change in uses chemical resins that must be periodically amphibian enclosures has greatly reduced regenerated or replaced. mortality and has facilitated successful Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London
46 AMPHIBIAN CONSERVATION
breeding of several species. However, the
open system has many benefits for maintain-
ing water quality and reducing pathogens,
while reducing system complexity, over
semi-closed systems.
The materials used to construct any water
system are important. Metallic containers,
vessels and piping should be avoided. In
particular, copper pipes leach copper into the
water and should be avoided, in both the
supply lines and filter systems. Inexpensive
PVC piping is easy to install and has few of
the negative aspects associated with metal
piping.
There are a variety of specialized plumbing
fittings that simplify the construction of an
aquatic system, as well as adding flexibility.
In particular, bulkhead fittings have a lot of
potential uses because they connect the
plumbing to the inside of an enclosure. This Plate 1. A common design for a canister filter. De-
piping can be used to provide influent, filtra- pending on the media installed, these filters can
tion or drainage to the tank. Pipes come in a provide mechanical, chemical and even biological
variety of nominal sizes and can be adapted to filtration. R. A. Odum, Toledo Zoological Society.
small or large systems.
different grades that correspond to the smal-
lest particle size they will remove. Pressur-
Filtration
ized water is forced through the cartridge
In semi-closed systems, water quality is where the particulate is trapped. Both these
maintained by continually treating the water types of filters will clarify the water effec-
with a filter system. There are three basic tively but fail to remove micro-organisms that
types of filters employed for aquatic husban- could be pathogenic. At best, this type of
dry: mechanical, chemical and biological. It filter will remove small filter-feeding organ-
is a good idea, in semi-closed systems, to isms but not their food (Wickins & Helm,
incorporate all three filter types to maintain 1981).
appropriate water quality. It should be noted It should be noted that while other types of
that although each filter type has its specific filters (e.g. chemical and biological) can also
function, it is not uncommon for a filter to remove particulate, this is not their primary
perform several functions simultaneously. function. In many cases, the ability of these
For small volumes of water, wad-type and other types of filters to remove particulate
canister filters are commonly employed for inhibits their primary function and greatly
mechanical filtration. These small units can reduces their efficiency. To prevent this pro-
be very effective in maintaining water clarity blem, a mechanical filter should be employed
and may also provide other types of filtration to remove the particulate so that the operation
functions. The medium used in wad filters is a of the other types of filters is uninhibited.
clump or a pad of polyester wool, which is Such mechanical filters are commonly incor-
inexpensive and easily obtained. Many types porated into filter-system designs.
of cartridge mechanical filters have become The earliest mechanical-filtration systems
available commercially for aquatic systems developed are the slow and rapid sand filters.
(see Plate 1). These filters employ a manu- These filters utilize fine sand as the filter
factured cartridge element that is available in medium, are more efficient than the wad-type
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of LondonWATER QUALITY AND AMPHIBIAN CONSERVATION 47
filters and can remove particles effectively versions of these activated carbon filters have
down to c. 6 mm with a sand diameter of been in use for many years to assist in
0 3 mm (manufacturer’s data). The slow maintaining water quality in aquariums.
sand filter functions by gravitational flow Activated carbon has unique properties
through the filter and is limited to a slow flow that make it an ideal material for amphibian
rate. Slow sand filters are generally very large enclosure chemical filtration. It is a highly
structures installed in large aquatic systems. adsorptive and porous material that readily
The rapid sand filter forces water through removes dissolved organic compounds, mi-
the sand under pressure and has a greater flow cro-particulate and certain reactive non-ionic
rate and, therefore, a larger capacity per size chemicals (e.g. free chlorine). It will even
than the slow sand filter. Commercially man- remove some ions, such as copper (Periasamy
ufactured rapid sand filters are generally too & Namasivayam, 1996; Seco et al., 1999),
large to be used in a small enclosure contain- although it is not as effective as other means.
ing below 750 litres of water. For larger The numerous pores create an effective sur-
enclosures, small swimming pools or hot face area exceeding 10 000 m2 kg 1 of car-
tubs, rapid sand filters are available commer- bon (Kinne, 1976). As water passes through
cially. There are also small to very large-size this porous matrix of activated carbon, organ-
units developed specifically for the aquacul- ic compounds loosely bond with the carbon
ture industry (see Plate 2). and are effectively eliminated from the water.
With all mechanical filters, suspended par- The porous matrix catches very small micro-
ticles are merely concentrated but not re- particulate (e.g. some bacteria), thus acting as
moved from the system. These filters must a fine mechanical filter, which can reduce its
be cleaned regularly to remove the physical capacity as a chemical filter if flow is inhib-
particulates or the organic components will ited. Activated carbon filters should always
decompose and chemically corrupt the water have a mechanical prefilter to remove most of
quality. the particulate before the chemical and fine
Filters that can remove dissolved sub- mechanical filtration by the carbon filter.
stances from water are considered chemical It is important to remember that chemical
filters. A common type of chemical filter that filter media have a finite capacity to absorb
is currently in many household is the water toxins and chemicals. The chemical media
purifier for drinking water. These filters will ultimately become saturated with toxins
contain cartridges with mechanical prefilters and, if they are not changed regularly, they
and activated carbon chemical filters. Larger will begin releasing those toxins back into the
water. Most chemical filters give no visible
signs of when this occurs. It is generally
recommended that chemical media be chan-
ged every 2–4 weeks but this will vary widely
depending on the amount of media in the
filter and the chemical load in the water. We
recommend the use of chemical filtration in
new systems or in systems with a known
problem that the chemical medium will ad-
dress.
The last type of filter is the biological filter.
It is perhaps the most important and the most
complex type of filtration in any system. Its
Plate 2. A simple rapid sand filter designed for whirl- action is neither mechanical nor chemical. Its
pool baths and small swimming pools is excellent for
filtering larger volumes of water. These are readily function is the accumulative effects of a
available from many sources. R. A. Odum, Toledo community of millions of living bacteria.
Zoological Society. Once this community is established in an
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London48 AMPHIBIAN CONSERVATION
enclosure, its actions appear unified, as if the PH
community was in itself a single separate MORE ACIDIC MORE BASIC
organism. A biological filter possesses many
1C 6 0 65 70 75 80 85 9 0 9 5 10
basic characteristics of life itself and, for the
purpose of this discussion, should be consid- 5 0 013 0 040 0 12 0 39 1 2 3 8 11 28 56
ered both as a community of organisms 10 0 019 0 059 0 19 0 59 1 8 5 6 16 37 65
15 0 027 0 087 0 27 0 86 2 7 8 21 46 73
(Hovanec et al., 1998; Burrell et al., 2001) 20 0 040 0 13 0 40 1 2 3 8 11 28 56 80
and as a separate life form that lives in 25 0 057 0 18 0 57 1 8 5 4 15 36 64 85
symbiosis with the animals housed in the 30 0 080 0 25 0 80 2 5 7 5 20 45 72 89
enclosure.
Biological filters remove the toxic nitro- Table 2. Percentage un-ionized (i.e. more toxic) am-
genous metabolic waste products of the ani- monia in aqueous ammonia solutions as a function of
mals and other organisms (e.g. decomposing pH and temperature (Florida Department of Envir-
onmental Protection, 2001).
bacteria) from the water in an enclosure. Most
totally aquatic vertebrates excrete ammonia
as a metabolic waste product. The primary bic bacteria produce toxic by-products, both
function of a biological filter is to oxidize inorganic (e.g. hydrogen sulphide) and or-
toxic ammonia/ammonium (NH3/NH1 4 ) into ganic (e.g. Clostridium), which could result
a less toxic form, ultimately producing the in a build-up of toxins that could kill the
nitrate ion (NO3 ). It should be noted that free animals that are maintained in the enclosure.
ammonia (NH3) is the most toxic form of Common types of biofilters that have been
ammonia/ammonium. The form of ammonia used for many years include the under-gravel
present depends on temperature and pH (see filter, the reverse-flow under-gravel filter,
Table 2). trickle filters and sponge filters. All these
This process of bacterial oxidation of am- have demonstrated their effectiveness and
monia is called nitrifying. It is not the inten- information on their function and setup is
tion here to discuss the details of the readily available.
biological processes that occur in biological One of the newer advances in biofilters is
filtration. Below is a basic equation of the the fluidized bed filter. These compact filters
overall nitrifying process (Lees, 1952): utilize the same basic technology as an under-
NH3 /NH4+1 NO2–1 NO3–1
Ammonia/Ammonium Nitrite Nitrate
Circulation through a biofilter is normally gravel filter with several major improve-
accomplished using pumps and airlifts. Water ments. A fluidized bed filter is usually in the
must flow through the filter at a medium-slow form of a clear plastic column 2 5–12 5 cm
rate in order for the bacteria to be able to in diameter and 0 3–1 0 m long, which
adsorb the nitrogenous wastes (Hawkins & usually hangs on the outside of the tank. A
Anthony, 1981; Wickins & Helm, 1981). The small pump, with a mechanical prefilter to
minimum flow rate is determined as the slow- remove particulates, injects water to the bot-
est flow rate that maintains aerobic conditions tom of the column. The water flows upwards
throughout the entire biofilter medium. If the through the column and overflows back into
flow rate is too slow or ceases entirely, the the enclosure. The flow of water is just great
filter will become anaerobic and will start enough to keep the sand suspended in the
producing ammonia rather than adsorbing it water column (fluidized) without forcing it
(Stickney, 1979). If this occurs, the nitrifying out of the filter. This sand provides a huge
bacteria will quickly die and be replaced by surface area for bacterial growth, and because
species that favour living in an oxygen-defi- it is constantly suspended in the water, the
cient environment. Many species of anaero- entire medium is aerobic and provides an
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of LondonWATER QUALITY AND AMPHIBIAN CONSERVATION 49
excellent base for nitrifying bacteria. These
filters are rapidly gaining in popularity and
replacing the more conventional wet/dry
trickle filters. One of the authors has used
Quicksands fluidized bed filters for years
with excellent results. However, fluidized
beds deteriorate rapidly when water ceases
to flow through them (e.g. during a power
failure).
Establishing a new biofilter is almost a
nurturing process that can take several weeks
to several months. The filter must be fed
ammonia and monitored through the process.
When fully established, a properly sized filter
is capable of oxidizing the ammonia load to
Plate 3. A biofilter cycling tank. Different types of
nitrates quickly, and there are no ammonia or biofilters, including trickle, sponge and fluidized bed
nitrites detectable in the system. Feeding the filters, are cycled in this tank using an artificial source
filter can be accomplished by using natural of wastes (ammonia). These filters can then be trans-
(animals) or artificial (dilute ammonia or an ferred to other tanks containing animals, without
cause for concern about transferring pathogens
ammonium salt) sources of ammonia. between groups. Note the instructions to the keeper
Nitrifying bacteria will also invade a me- for daily maintenance on the left side of the tank. R. A.
chanical filter and function as a biofilter if the Odum, Toledo Zoological Society.
flow rate is not too rapid. Certain types of
mechanical filters provide the appropriate It is a good idea to always keep a few extra
conditions for biofiltration better than others. biofilters going in tanks with heavy simulated
One of the best is the slow sand filter. bioloads (see Plate 3). The filters can be
attached to a disinfected tank and liquid
Maintaining a biofilter household ammonium (with no detergent or
perfume), added daily at a rate of four to five
Again, the biofilter should be thought of as a drops per c. 38 litres of water. The water must
living entity in an enclosure. The bacteria be daily monitored for ammonia, and the
must be supplied with a constant flow of amount of household ammonia added can be
oxygenated water at the appropriate tempera- adjusted as appropriate. In this way, when a
ture, which contains low levels of ammonia new tank is set up, an established biofilter is
and nitrite as food. Without these necessities, available without having to wait for a new one
the filter will suffocate and starve. If the tank to cycle. This filter should be free of potential
must sit idle (without animals), move the pathogens because it has not been in contact
biofilter to a tank with animals to keep it with a system that contained animals. This is
going, or simply feed it ammonia every day. vital for that unexpected batch of larvae. Also,
Also, attention must be paid to the amount of if appropriate precautions are taken, these
time a biofilter is shut down during servicing. filters could be used in a biosecure situation.
The longer it is down, the more bacteria
suffocate and the less effective the filter will
Plants
be until it recovers. Do not clean a biofilter
excessively; just rinse the media if and when Another often-overlooked form of filtration
necessary. Never use chemical disinfectants (bio and chemical) comes with the addition of
on a biofilter unless you plan start the initi- living plants to the system. Plants help to
alization process again. Antibiotics can also remove organic as well as inorganic waste
kill a biofilter, so always treat sick animals in from the water and are a great source of
a separate ‘hospital’ tank if possible. oxygen. Some aquarists use only living plants
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of London50 AMPHIBIAN CONSERVATION
for filtration. Plant-based filter systems are Water changes
so effective that they can even be used for
Regular water changes are essential to rid a
treating human sewerage (Levy, 2007).
system of the minor toxins that are not
Furthermore, plants greatly enhance the attrac-
managed (like nitrates and phosphates), and
tiveness of an aquarium and provide oviposi-
to replenish any nutrients that were absorbed
tion sites for many amphibians. If the
by the plants and animals. A minimum of
inhabitants of the tank are large or active and
10–20% water change every 1–2 weeks will
tend to tear up rooted plants, it is possible to
generally suffice.
culture plants in a separate tank adjacent to the
animal tank, and use filters to pump water from
one tank to the other. Just letting the tendrils Waste-water management
of a potted plant, like Pothos Epipremnum
aureum, dangle into a tank can significantly With the realization that diseases spread by
reduce nitrogenous wastes, especially nitrates. human activity have caused declines, and in
some cases outright extinction of amphibian
populations, considerable attention should be
given to how waste water from amphibian
Water testing facilities is disposed of (see also Robertson
Water testing kits and devices are readily et al., in press).
available from many sources. They vary from
simple colorimetric systems (e.g. dip sticks,
CONCLUSION
cells) to highly sophisticated and accurate
spectrophotometers (i.e. like those manufac- Understanding water quality is essential for
tured by Hach). In most cases, the simple the long-term successful breeding, rearing
colorimetric systems are adequate for the and maintaining of amphibians in captivity.
amphibian keeper to monitor water quality Proper monitoring of water can establish
and diagnose problems. When a system is negative trends in aquatic systems before
initialized, the water should be tested fre- problems arise. It is often the case that the
quently. Once established, it can be moni- damage is done before an increase in mortal-
tored less frequently. Ammonia/ammonium, ity and morbidity is observed.
nitrites, nitrates, pH, hardness and phosphates When a problem is encountered, the water
are tests that should be performed, at least quality should be tested (along with other
initially. It is highly recommended that the possibilities) to determine if there is a cause-
primary water supply be monitored occasion- and-effect relationship. If eggs or larvae die,
ally. Municipal water supplies frequently water quality should be one of the first areas
change their chemical composition depend- examined to find a possible cause. If mortal-
ing on the situation of their supply or for ity in adult amphibians is a problem, check
maintenance (i.e. water-line repairs usually the quality of the water supply. If a relation-
are followed by higher concentrations of ship between water quality and mortality or
chlorine to disinfect the lines). health problems is discovered, improve the
Without water testing, the amphibian kee- quality of the aquatic environment. The solu-
per cannot know the quality of the water they tions to water quality problems are many and
are providing for their animals, making them answers are only found by applying the
oblivious to this most important aspect of principles of water management.
amphibian husbandry. Many of the signifi-
cant and commonly encountered toxins in
aquatic systems are in such low concentra- Checklist for a healthy aquatic system
tions they cannot be seen nor do they have a Start with high-quality water.
smell. Testing is a better strategy than mere Filter the water three different ways: me-
faith that the water is ‘good’. chanically, chemically and biologically.
Int. Zoo Yb. (2008) 42: 40–52. c 2008 The Authors. Journal compilation c 2008 The Zoological Society of LondonWATER QUALITY AND AMPHIBIAN CONSERVATION 51
Clean mechanical media at least weekly, Micropterus salmoides). Journal of the Fisheries Re-
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Where possible, incorporate live plants. teria for water, July 1976. Washington, DC: U.S. Envir-
Perform water changes often. onmental Protection Agency.
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water: Storet Parameter Code 00619. Tallahassee, FL:
Florida Department of Environmental Protection. ftp://ftp.
PRODUCTS MENTIONED IN THE dep.state.fl.us/publabs/assessment/guidance/unnh3sop.
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