I know this isn't what we are talking about in a chameleon forums, but a properly set up waterfall is not necessarily bad for all herps, and neither is bacteria.
Bacteria are a key component of biological filtration in a fish tank. A similar effect to the effect an undergravel filtration plate has in a fish tank can be achieved in tanks for small herps. I used to use waterfalls all the time in dart frog tanks for example, and these would work just as well for small day geckos or anoles and the like.
The method is this- a deep substrate of gravel or hydroponic clay balls (several inches is best, but with small frogs and the like just enough to cover the pump). On top of that layer put fiberglass window screening, and on top of that put whatever you are using for "earth" (coco fiber or peat moss for examples). Except in the area you want your waterfall. Beneath the base put a layer of gravel all the way down to the fiberglass. Put this area on the opposite end of your tank as your pump. Stack some big rocks (or place a single large rock) up on top of the gravel base. Run your water tube from the pump to the top of the rock pile. Add your water and turn on your pump.
Water is drawn from the pump, spills over the rock pile for the waterfall, drains through the gravel base and into the bottom level of substrate, then is drawn through the gravel base substrate all the way across the tank to the pump again. Beneficial bacteria grow in the gravel base and clean the water as it flows through the gravel.
This can further be improved upon if you have some plants who have roots that reach down into the bottom layer of gravel.
Get a book on aquarium filtration to understand how it all works.
This system can even be used for medium sized lizards- I once set up a 125 gallon tank for a pair of green basilisks that had a waterfall on one end a pool at the other end, with lots of live plantings in and out of the water. Once every week or two I would siphon the water out of the pool end and replace much of it- just like anyone would do for a fish tank. Never had a problem and the basilisks bred like crazy in there.
I doubt any of this is useful for chameleon enclosures though.
It doesn't apply to the little plastic self contained waterfalls either because you cannot draw the water through a large volume of gravel - you need a pretty good volume of gravel and water drawn through it for the bacteria to do their job and clean it.
But if the other forums you are on is for frogs or smallish lizards, if they are using a setup like I am describing, maybe my description helps explain the hows and whys.