Caring for Selected Otter Species (Asian small-clawed, Cape ...

was provided in tubs for the animals to bathe in. Regardless of water treatment method used, an additional source
of fresh, potable drinking water should be available at all times.
Water quality should be maintained at a level sufficient to control bacterial counts and organic load, and
to allow clear underwater visibility of animals for health inspections. Clarity and color maintained to provide a
perceived color of clear and/or blue water is preferred by most facilities. This water clarity is an aesthetic
requirement only, as long as the water quality is maintained, and the presence of floating algae or other material is
not harmful to the otters.
Otters can be messy eaters and will track a lot of particulate debris into their pools. All food remains should be
removed from pools daily to prevent consumption of spoiled items. The filtration system needs an effective means
of skimming (from top to bottom) particulate matter. Turn over rate using rapid sand filtration is suggested to be
once/hour; meaning that the total exhibit water volume should be turned over at least one time per hour when
using rapid sand filtration. When using rapid sand filtration couple with Ozone; the turnover rate can be extended
to once every 1.5 hours.
Ozone applied through a contact chamber in conjunction with a low dosage of chlorine is an effective
treatment for freshwater systems. A large surface area biological filter bed should be incorporated if possible. This
will allow a natural nutrient removal system to establish itself, which will provide system stability. It also will help
reduce organic loading as well as reduce colonization of undesirable bacteria species. The tank effluent should be
pre-filtered before it is sent to the sand filters and foam fractionators.
At least bi-weekly water quality tests are recommended for bacterial counts and daily tests of chemical
additive levels. Records should be maintained and available for APHIS inspection (in the U.S.) and reference if
problems arise. All appropriate regulatory agencies should be consulted in other countries.
Coliform bacteria: Coliform bacterial counts are used to monitor filtration system efficiency and keep
track of potentially harmful bacteria. Coliform counts should be done at least every other week and more often if
there are multiple animals using the pool (a policy regarding coliform testing should be set by the institution).
Often a MPN (Most Probable Number) per 100ml is given as an acceptable limit. However, a more accurate
measure is the total or fecal coliform count (NOAA 2006). There are no standards yet established for fresh-water
otter pools. At this time, it is suggested that coliform levels be maintained at or lower than levels established for
rescued pinnipeds by NOAA. These are:
- Total coliform counts should not exceed 500 per ml, or a MPN of 1000 coliform bacteria per 100ml
water.
- Fecal coliform count should not exceed 400 per ml water.
If animal caretakers are routinely exposed to pool water, an institution may establish a higher standard of
100 per ml, which is the level considered safe for humans; this should be based on institutional policy.
Chlorine: Many municipalities add chlorine to their water, and readings from tap water of 1ppm or higher
are possible. While otters generally show no adverse effects from these levels, it is not known what the overall
impact is to their health and the water repellency of their coats. For this reason, the AZA Otter SSP recommends
that otters should not be exposed to chlorine levels higher than 0.5ppm for prolonged periods, and ideally chlorine
should be kept at a non-detectable level. The addition of sodium thiosulfate will neutralize any residual chlorine
(see below and Appendix H).
Algae control: Algae control is a continuing problem in otter pools, particularly those exposed to
significant sunlight. There are several techniques that have been used with varying success (see Appendix H).
- Liquid copper sulfate: Liquid copper sulfate can be added directly to the pool water without harm to
the animals. While this does not get rid of algae, it will inhibit algal growth.
- UV sterilization: Ultra violet sterilization has proven helpful in inhibiting algae build-up, particularly
when combined with regular cleaning of pool sides.
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