I have a 20 gallon tank with 6 platys and 2 rasboras. I got the platys because I wanted to start raising fry to replace fish that die off. I have a mesh breeder tank which I had been putting in the fry - it's designed to float so that the lip is always above the waterline. However, one morning I found one of the platys had somehow gotten in to the breeder tank. The two smallest were gone (fish food I assume), and the larger one was dead, probably nipped or scared to death. I took the platy out, but found it in there again the next morning! Do platys jump? I've never seen that behavior, but that's the only explanation, as I took the breeder tank out and there are no holes for her to slip in. Hopefully she gets knocked up to replace the ones she killed.