After the thousands of suggestions to members about NOT having a waterfall in enclosures it is not a bad question. The difference is that in your case the bowl (I'm assuming) is easily removable and can be cleaned on a regular basis. Yes, very hot water, and some mild dish soap should be fine!
The problem I find with water bowls of any type is when we as owners get "lazy" and skip cleaning them. (This becomes even more likely if it is difficult to get to.) I've been known to skip emptying my catch bucket for my misting system from time to time...
sniff,.....sniff,.......excuse me for a moment...(
SPLASH)........
and it can get pretty messy and disgusting!
Remember that there is no one answer to any question, and just because it is a general rule doesn't mean it is the only way. I will say, in my experience with many reptiles, chameleons do offer some more unique challenges than quite a few other types, so I don't think I would just assume what works for one works for all.
Good heavens- do you guys have lizards besides chameleons? Or other pets? Do you think something magic happens when a water bowl is put into a chameleon's cage that doesn't happen with any other animal's water bowl?
The only time something magical happens is when I accidentally use one of my enchanted bowls. Of course nothing magical would happen from using just a regular bowl.


