Hi Everyone, First time posting here. We are new fish owners (and really enjoying it) and here is our setup: We have a 20 gallon tank currently with 4 female platyfish and 2 swordtails (1 female and 1 male. we are getting a new female but we want to wait a week since we just introduced 3 new fish about a week ago). We have live plants. I'm sorry but I can't tell you what kinds, just that the owner of the local fishstore in town assured us they would be fine with our platys and swordtails. All the fish seemed to be behaving well together and acting normally until today. The problem: One of our females started hanging out at the bottom of the tank today. Noticed it a couple hours ago... and every now and then she tries to swim... by swim she just kind of twirls. She can move around but it's extremely erratic and she kind of constantly is moving towards the ground, all the while twirling. After one of these little sessions she just lies for a bit. We have taken her out for now... Not sure what to do! Any advice would be greatly appreciated.