Hi there, my husband loves fish and recently got a tank from a friend of his, in this tank we have 2 black widows, several assorted platys, a placostamus, albino sucker fish, 2 barbs and a zebrafish. anyway, with the platys giving birth and all of that he bought a second tank for the mommy fish to have the babies in. once he had the tank running for a few days he put the zebra in it to regulate the water or something like that. anyway the zebra was fine in that tank, though he did look a little fat, we just assumed that was from eating too much, but about a week after putting him back in the big tank he's gone strange. His stomach is really swollen and his back which was streamline and straight has now gone skew. I dont know what is wrong with him or what to do bout it. can anyone help.