I have a (what I believe to be) male veil tail betta fish in a 5 gallon Fluval Spec V aquarium with the built-in filter and a separate heater. I don't know what age he is but I received him in May and he appears to have grown in size a little bit since I first got him. He's a happy-go-lucky personality and very curious, exploring every inch of his tank and every decoration/piece of equipment (heater, thermometer, etc.) He doesn't usually flare unless you go up close to his tank while he's in the middle of blowing bubbles for a bubble nest or if you leave your finger in too long when you feed him. All that being said, now on to my problem. Yesterday, around 4:30pm I noticed that his right side ventral fin was missing a large piece of fin tissue and the bone was exposed. Upon further inspection, I noticed his right side pectoral fin was shorter than the left side one and he was not using it to swim around his tank and mostly kept it clamped to his body. Otherwise, he was not displaying any other worrying symptoms. He ate 2 small New Life Spectrum Betta Pellets that morning and was swimming around all over his tank as he normally would. In fact, if I hadn't noticed the ragged end of his ventral fin, I probably would not have known something was wrong. I know he has a habit of letting the filter intake "suck" him up to the wall of the tank and believe it or not he sleeps up there when I turn his light off. I think he likes being able to be suspended up there and he just lifts his mouth up to the surface for air. He usually has no problem unsticking himself from the intake wall but I have a feeling that the sponge on the other side fell below the water level and made the suction more intense than he's used to and he must have had to struggle to pull himself free. I feel so bad about it because I should have done a water change the night before and I would have noticed that and pulled it up but I put it off one more day and I'm kicking myself now because I feel like this wouldn't have happened if I had just done it! Anyway, after I saw the fin damage, I did a 100% water change to make sure the new tank water was clean and treated it with Seachem Prime. I had read some different opinions online and went to Petco to get some API Stress Coat to help regrow his fin tissue. I added the stress coat to the clean water and returned the fish into his tank when the water temp had reached 79 degrees F. Usually his tank stays around 77.8-78 degrees F so I didn't want to up the heat to 80 or higher when he's not really used to that temp. He ate 2 pellets this morning once he got back in the clean tank and continued to swim around as if he was not in any pain, although he definitely is not using his right side pectoral fin at all to swim. I ordered Kordons Fish Protector and Vita-Chem from Amazon and should have them delivered by Friday. I also purchased Aquarium Salt from Petco but have not used it after reading conflicting opinions online as to whether it can do more harm than good. Can anyone tell me if there is anything else I can do for this poor little guy to help his fins grow back? I'm a little worried because yesterday he still had some tissue on the ventral fin and this morning it's completely bare and just his little bones are left! I don't believe it to be fin rot, because none of his other fins are affected. Thank you for your help!