kageotogi

Sort of. The people who had any idea at all said it was probably either something in the water (although when I told them it was spring water, they retracted that idea) or some sort of algae. Basically all I have to do is soak the tank in hot water for a bit and it'll solve the problem temporarily. In any case, it's not something to worry about so I'm not going to conern myself with it. ^_^