Hello, I am new to this forum and would like some opinions about my Betta's fins. I bought this Betta last April, I had him on his own in a 5 gal for many months and he was doing well. About 3 months ago I decided I wanted to upgrade my aquarium to a 10 gal I put the Betta with 3 julii cory and he was doing great, little to no aggression issues Since then I have added 4 black neon tetra and 4 von rio tetras. About 2 weeks ago my Betta stopped eating and exploring the tank. He would sit on the bottom in the corner all the time, only coming up for air when he needed. He was like this for about a week, but now he is back to acting like himself and I'm not sure what was wrong with him. He is eating and swimming around like he used to and he appears happy to me. He doesn't attack his tank mates and they all pretty much stay out of his way. But now that he is up and swimming again, I noticed his fins look in bad shape, here is a picture of him today. Imgur: The magic of the Internet This was before he stopped eating and being active. Imgur: The magic of the Internet I know this picture is a bit blurry, but you can see his fins looked pretty good. Is this fin rot or from stress? When I upgraded to the 10 gal I placed only silk plants to prevent any fin tears. I have a heater and keep the water at 81 degrees constantly. The tank is cycled and all the other fish are doing great. I do weekly water changes of about 20 - 30%. They say with fin rot you will see black or bloody fin tips, but I can't really tell if there is any blackness. Did I add to many tank mates for him and they are causing him stress which made him ill? Thank you!