Why is my molly swimming like this?

[nikitar]

Hi All, I'm pretty new to owning a fish tank I have a 200L tank. I have had it for 3 months and I brought 2 Mollie's a month ago my black and silver molly has been swimming vertically at times. I have read that it could be a bladder disease but I'm not to sure. Can someone please help me. Here are some pics one of my tank and others of the molly thank you in advance


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[nikitar]

Also the orange molly you can see in the second pic always chases the black molly.
Could this have anything to do with it?


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[ghostshrimp92]

My silver and marble mollie did that for about a week or so when I first got them they would swim like that than shake. I've had them for 4 months now an haven't seen them do it ounce. I hope that kinda helps I'm sorry I'm somewhat new at fish keeping


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