Is it slimy? I have noticed a white slime forms whenever I use plastic enclosures, such as large pails, to overwinter minnows. Since your enclosure isn't plastic, I'm wondering if it could be coming from the other plastic elements inside the enclosure, like the fake plants. But, this could be something completely different. What I've seen in my case is a white slime-like substance that forms on the surface of the water, but my enclosures were not transparent, so I can't say for sure that there weren't specks inside, too. Although I had pumps in the pails, the only way I was able to keep the slime from forming was to disturb the surface of the water with agitation from a water pump or air bubbles (anything that would keep the surface water constantly moving), which, I realize, isn't a good solution with an Axolotl. I don't know if this could your problem, just adding my own similar experience. (BYW, this happens in the plastic pails I overwinter for plants, too, that have nothing in them but rain water caught in the fall, so it's not coming off the fish. I've bleached and rinsed the plant-water pails prior to filling them each fall, kept them tightly covered/out of light, and while that slows down the slime, it still happens, but only when using plastic containers. I don't mess with it in the plant water pails, just get rid of it in those pails that house fish. It doesn't seem to harm anything, plant or fish, but it's GROSS.....slimy and icky!)
