Help! Sudden clamped fins!

Hello!

I got a new betta about 3 weeks ago. My tank is cycled an it is reading either 0- .25 ammomia and 0 Nitrites. It does have nitrates but I haven't checked the reading since I got him.

I'm not sure what has happened. I got a new heater so the temp is always around 75-80F and I do 25% water changes every week. Suddenly his fits are ridgid and he is hiding everywhere. When he moves he is darting about the tank and his body looks frozen and rigid, not fluid like most betta. He still has an apatite and I feed him every other day about 4 pellets (not sure if that helps?). I'm not sure what I'm doing wrong.

His name is Bowie, I had high hopes for him .

Hi!

I would try to keep the temperature at 78F, and have it constant, not in a range like 75-80. I feed my bettas twice a day, 2-3 pellets in the morning, 2-3 at night. Make sure his diet has a lot of variety. You can feed him brine shrimp, blood worms, cucumber, as well as the pellets.

Good luck!

edit: What size is your tank?

If it helps any, when I first got mine a couple months ago he was like that and would flare at the heater and hide behind the filter. He eventually got used to his surroundings and goes where ever and only flared at his tankmate, a snail.