Hello and thanks for any help. I have an established tank now for the past 4 months. Everything seems to look ok. The water quality is good. Tank is crystal clear.I have 2 Platies along with some other community fish. I have not been able to determine the sex of the two. One is significantly larger than the other and chases the small one around constantly. There is definitely at least on female as I had babies already. Two babies survived and are very healthy looking..about 2 months old.All the fish are eating including the distressed one. The problem is, she doesn't look good at all. I found her lying on the bottom of the tank. Then, she was swimming around darting back and forth. Then, back on the bottom. I put her in the net breeder tonight thinking this may be stress induced. Could the supposed male be exhausting her? She seems to have decent energy as I had a hard time catching her. Probably caused more stress..I hope she is ok..any suggestions? I have grown very fond of her..it would be sad to lose her. I don't see any visible signs of disease and the other fish all look fine.Thanks Again, Elaine 
