Hi all,

I use an air pump & stone in my frogs water bowl to create humidity, it works great.
Usually the bubbles rise to the surface of the water and disappear, but sometimes - very rarely, the bubbles don't disappear and congregate on the surface of the water like foam. This happened yesterday so I changed the water and it went back to normal but then a few hours later the foam was back. The air source is outside, and there is nothing in the water accept for water. I'm wondering why this happens - i tried to find info on the net with no luck.
My frogs don't seem to mind the foamy bubbles at all.
Is it a temperature thing? Something in the air? Or what?
Anyone know what causes this?

Jess