My new betta is very poorly
and I don't know why. His fins have become ragged - like fin rot and he spends a lot of time sitting on the substrate.
The water parameters are good, no ammonia, no nitrites and low levels of nitrate. I do regular water changes once a week. He has no other tank mates in his 10 gal tank, so he's not been bullied. I can't seem to find out why he's like this. I've added some fin rot medication to the water and tomorrow I'll do another water change and add some more. Has anyone any ideas as to what went wrong.

