I think it depends a lot on your set up. Most of us have false bottoms/drainage layers so it's not necessarily practical to stick an undergravel filter in there, and you may not have any gravel at all (in the case of a false bottom).
I think that with amphibians that are being misted regularly and often in a viv with a recirculating water feature, the act of flowing down the feature, into the pond, then into the false bottom provides a lot of biological filtration (it does depend on your bioload.) Also, if the tank is being misted often, a lot of the water is being replaced over the course of a week.
If supplemental filtration is needed, I always like the sump with a wet dry trickle filter for ease of set up and maintenance. It's really cheap (you can make them out of plastic containers of any size,) and you can service it without tearing apart your tank.
If it's not practical to have a second container below your viv for a sump, maybe an undergravel filter may be a good option. I'm avoiding any major water features for a while though. I'm tired of leaky plumbing, moving buckets of water, etc.
Thanks for your response. Good point - recirculating water can definitely function as does an undergravel filter - oxygenated water moving over a substrate is all that is required. I've done a few along those lines at the Bx Zoo, for poison frogs and temperate zone salamanders.
Trickle work very well also; I'm glad to see more people are considering them f use with herps.
I am using a ug in a tad grow out and it works very good. (see last pic.)
FYI, using UG filters tend to cause the water pH to drop due to the enhanced biological activity... whether in a fish tank or herp set-up... so its is something to keep an eye on.
Also, I have been using UG filters as false bottoms and they are great. If you leave a lift tube in place... cut to substrate height, and cap/ plug it... it is so simple to stick a siphon down and drain the viv. Good alternative to drilling if you don't need a constant drain.
I have added a few pics that should be self explanatory
Oh good call on a tad tank. I'm usually a minimalist when it comes to equipment and maintenance... there's a term for it in planted aquaria that I can't remember. But any way, that definitely seems like it would work well!
Thanks...actually I've used live plants to help with water quality in tadpole tanks; many prefer /dead/decaying plants to living. Tough-leaved types such as water hyacinth/lettuce, and most grasses, work well.
Great idea on the false bottom - especially for one as unskilled as I in creating my own, thanks! I found pH to fall in a wide variety of situations - I suspect it occurs more commonly with UG filters because detritus remains unseen in the filter bed and gravel-washing tends to be put off if the water looks clear. Outside filters slow down more noticeably, forcing folks to clean them regularly.