Water feature for a small vivarium?

[killerecho]

I need help implementing a waterfall/pond area in a small tank (10-20 gallon). I've combed through all the info I could find on this forum and others but have yet to find a clear, conclusive idea. I've tried a number of methods and failed, with the water quickly becoming stagnant and polluted or leaking into areas it didn't belong, flooding the substrate.

The vivs I want to add water areas to have false bottom hydroton layers and live plants. They will house gray tree frogs and pacific chorus frogs, which will presumably dip in the water nightly (and defecating copiously). A waterfall would be great but not absolutely necessary. I would just like a shallow pool - 1-1.5 inch deep. I would prefer not to drill holes in the glass if possible.

I guess it boils down to 3 questions: what's the best way to do this; how often does the water need changing; and what equipment do I need?

Thanks for any advice you can share.

[Iratus ranunculus]

The hydration layer makes this a lot easier than you think. Any flooding or leakage will just drain back into it. It is not a big problem, provided you have a good naturalistic substrate which is biologically active. The easiest solution would be to build a stream course that circulates the water in your hydration layer. You can do this with rock and gravel, and aquarium sealant.

First, build a filter you can remove and clean. You can do this with, say, wide diameter PVC pipe in two layers, a pump, a drill, and filter media of choice. Get a piece just wider than the pump, drill holes in it, then place a larger diameter piece (also with holes) around it, with filter media in the space between them.

place this in a hole in the false bottom. It will recirculate the water from the hydration layer (which presumably will have some biological filtration media like gravel or hydroballs).

Then you can build a waterfall. I would recommend using using cork bark (the natural pieces) siliconed together to form a box, or rock used the same way. You can then say, drill a hole to insert the tube for the pump, allowing the water to trickle down the channels in the cork (you will need to pick a good piece for this, or carve out a proper channel). This box can then simply be removed, and the filter media changed at will, and you can change the water using the pump. I suppose the waterfall could also be constructed using expandable foam.

A stream course can be constructed from rock siliconed together and sealed and then inserted into a trench in your primary substrate, draining into a clay dish (the type used with potted plants). They have a hole in the bottom that can be used along with a short length of aquarium tube as a drain back into your hydration layer (just cover the hole with screen to prevent clogging)