We have had fish now for about 4 months, but we just set up a 40 gallon tank about 4 weeks ago. There are mollies and guppys and 1 gold algae eater in the tank. One of the mollies has started swimming vertically with her tail up and head down. When she is swimming away from stuff like a net or other fish she swims fine. But when she is just swimming or sitting on her own she is vertical. Any advice?
Well the molly I originally posted this about died the next day. We got two from a friend out of the same tank, and both of them were swimming funny. So we took them out (a gold one and a black one) of our 40 gallon and put them in a 10 gallon with a Betta and two endler guppies. I looked on here and saw an old post that said to do an epsom salt bath (70g of salt to 4 cups of water). We put both of them in the bath, because after about 3 hours in the 10 gallon the black one started going vertical on the bottom of the tank. They both did much better after the salt bath, until that night and then the gold one was swimming vertical again. So the morning of the 31st we found the gold molly dead, but the black molly was still swimming normally. Probably 4 days ago, the black molly started swimming vertically and she became very skinny. Well, 3 days ago in the afternoon I saw a dead baby in the tank. So I went and got a net and a turkey baster to catch any that were still alive. We did find 2 molly babies and about 5 endler babies, but only 4 made it out of the tank. So after that we thought she would straighten up, but she didn't and she died a couple of days ago. She wasn't eating at all, so she wasn't going to the bathroom. But since then everybody else is doing fine, so it must have been something caused in my friends tank because all of our original fish are doing fine.