Betta swiming in circles

Question
I have 2 betta's and they are in a tank that divides the two.  One of the fish is swimming in a circle and chewing on the back fin.  It is lying on its side, very sluggish. I change the water 2 times a week.  I do not take the fish out when I drain the tank, I use a tube to drain the water then I replace the old water with clean using 8 drops of aqua safe drops per gallon.

Answer
Hi Aurea;

He may have a failed swim bladder. The swim bladder is an organ below the spine inside the fish that controls buoyancy, or basically the ability to float. If it fails, the fish can't stay upright in the water and will sometimes lay down. It can fail for many reasons, but the only treatable cause is for a bacterial infection. We usually try "Maracyn 2" by Mardel to see if it helps. The problem is that even if the infection is cured, the swim bladder may not regain it's ability to function. It has to heal and often they don't.

There are other causes such as viral infection, genetic deformity, cancer, temperature shock, stress, unhealthy diet or overfeeding, etc., but the effects of these causes aren't treatable once the bladder fails. You just have to wait and see what happens. Prevention is simple though. Keep the tank clean (which you are already doing), keep it warm, put the same temperature of water back in the tank when changing water, avoid stress and provide the fish a good healthy well-balanced diet without overfeeding.

Followups Welcome

At Your Service;
Chris Robbins

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