I have a 10 gallon tank with one goldfish and two apple snails in it. Well, there were two. They have been in that tank for about 2 months. I have done water changes frequently but never over 50 %. Recently I have noticed what I think is algae growth, although it is kind of brownish-green, and popped up suddenly. It is all over everything. I have cleaned it off and it is back in a couple of days. The water parameters are fine, and the goldfish is doing wonderfully. A few days ago one of the snails crawled out of his shell and then just disappeared. Last night I noticed that the other one had crawled out of his. He is still there and alive though. Any idea whats going on?