It is still considered standing water because it's not going through a filter that would keep the water clean. Water, even trickling water, in a warm moist environment is going to grow mold and bacteria if it's not filtered or cleaned regularly (as in daily). And it just takes a piece of shed shin, a stupid cricket falling in it, your chameleon pooping in it, etc. to introduce a raging bacterial problem. And then with the water trickling it is aerosolizing that into the air, where your chameleon will breathe it. Or heaven forbid actually drink it! Even without direct contamination it still grows stuff all on its own due to the nature of the environment. So the sound of it is nice, but that's about the only pro to it. Lots of cons. It is the general consensus that you should not use them in chameleon cages for those reasons.