Aquatic Stream Enclosures

Complex Aquatic Stream Enclosure. The aquatic stream enclosure is suitable for amphibians adapted to living in well oxygenated, usually cool streams with a significant current. Typical species include the stubfoot toads, Atelopus spp., the tailed frog, Ascaphus truei, the hellbender, Cryptobranchus alleganiensis, and the larvae of many stream-dwelling and riparian salamanders, such as the American brook salamanders, Eu- rycea spp., the spring salamanders, Gyrinophilus spp., and the Pacific giant salamander, Dicampton ensatus.

The basic stream enclosure (Figure 5.3) has a false floor overlayed by gravel, similar to the pond enclosure. The deep area of the stream should have underwater caves and crevices where the tank occupants can seek refuge, as well as shallow water areas where the amphibian can rest and gulp air. Depending on the species, the water may be shallow throughout, allowing the amphibian at any point to reach its head up to gulp air while keeping its feet on the stream floor. There may also be exposed land areas, if appropriate for the species.

Figure 5.3. Lateral view of stream enclosure for amphibians. A. cross-section of board supporting the rim of the tank, tipping it toward the water outflow end. B. false floor assembly (see Figure 5.1 В—D). C. pea gravel layer approximately 5 cm (2”) thick. D. underwater rock cave. E. shallow water rest area. F. partially flooded rock cave. G. waterfall. H. hose fitting to spread the water flow. I. water outflow from the canister filter. J. hole in the tank wall just large enough to pass the canister filter tubing. K. lid (see Figure 5.1 E—H). L. golden pothos, Epipremnum aureum, a hardy vine able to live “rooted” in water and tolerant of considerable root disturbance. M. emergent rockwork covered with moist sheet moss. N. water inflow to the canister filter. O. water line. P. drain assembly (see Figure 5.1 К—M). (Sandy Barnett)

Unlike the pond tank, the stream enclosure has a moderate to strong power filter for rapid water turnover. It is set up so that it provides undergravel filtration, in addition to cycling the water through an outside canister filter or powerhead.

Outside canister style filters are preferable to intank models on amphibian enclosures. Outside filters are less work to remove and clean, and a shutoff valve on the supply hose allows the filter media to be changed with a minimum of disturbance to the animals. A trickle filter addition on the return water can further increase filtration and dissolved oxygen levels.

The outflow from the canister filter can be used to create a waterfall. A waterfall adds aesthetic appeal, can provide additional underwater and terrestrial habitat for the animals, and helps oxygenate and biologically filter the water. A waterfall can also serve to channel or disperse the force of the water current, depending on the configuration of the rockwork. Many stream-dwelling amphibians fare better in enclosures with a current. The hellbender, Cryptobranchus alleganiensis, seems to prefer an enclosure that provides a current strong enough to ripple its skin folds. The animal will rock from side to side if a current is not provided, presumably to better oxygenate its skin for respiration. If a current is provided in an enclosure, some of the underwater shelters should be arranged perpendicular to the current so that areas of calm water are available to the animals.

If the water intake for the canister filter is located above the substrate, care should be taken to screen the opening so that the amphibians cannot be trapped by the force of the filter’s suction. If feces need to be collected for parasite examination, the canister filter may be temporarily removed, and the dump and fill method used to maintain water quality. A strong air pump can be temporarily added to the setup, similar to how it is used in the aquatic pond tank, to keep the undergravel filter operating and healthy during the down-time for the canister filter. An airstone can also be placed in the main water body to further oxygenate the water. If the canister filter is left off for more than a few hours, it should be broken down and cleaned before reuse, as anaerobic bacteria will grow and render the filter media unfit for use.

It may be difficult to find aquatic plants that will thrive in a stream enclosure, due to the strong water current and uprooting by the tank occupants. Golden pothos, Epipremnum aureum, a very hardy creeping vine, can be anchored without soil to emergent rock- work or a dead branch, and trailed into the water. It will not only filter the overhead light and provide cover for the tank occupants, but it will also help to clean the water, removing harmful wastes.

Amphibians adapted for living in a stream habitat generally require water that is highly saturated with dissolved oxygen and contains undetectable levels of ammonia or nitrite. Stream dwellers are extremely sensitive to toxins and pH fluctuations. It is recommended that ammonia-absorbing resins be used in combination with activated charcoal in the filter. Also, partial water changes (10-20% weekly) are highly recommended. Large debris should be siphoned out daily.

Spartan Stream Enclosure. A much simplified version of the stream enclosure may be advisable. Such a spartan enclosure has no substrate. It has simple rock or PVC pipe retreats, and a land area made from piled rocks, sheet plastic, or styrofoam. Water quality is maintained with a canister filter. Such an enclosure is easily disassembled for cleaning and disinfection.

There are many species of stream-dwelling amphibians that do poorly in a spartan setup, even on a temporary basis. Larvae of the Pyrenees Mountain salamander, Euproctus asper, do better when maintained on a gravel substrate than on a barren floor (Wisniewski, 1986). Possibly the substrate allows the larvae to rest in more ergonomic positions than those larvae deprived of the substrate.