Thank you so much! Its my female betta, Claudia with the ripped fin. I cleaned her tank just now with a sponge, scrubbed her gravel and all decorations, and put water conditioner in it. I'm heating it back up with the heater and waiting to put her back in until it's reached his proper temperature. I will have to go get some salt and some stress coat. I rescued a betta today from a petstore, but he's a crowntail so its hard for me to tell if he has fin rot or anything bad because of his fins being the typical crowntail style.