Hi Guys, My poor Betta fish is having such a hard time with Fin Rot and I'm at my wits end. He is in a filtered, cycled 5 gallon tank with a temperature pretty consistently at 80. Ammonia is always between 0 - 0.25 (I'd say about 0.10) (My tap water has ammonia of 0.25 and PH of 7.6 so I mix half and half with spring water and use Prime water conditioner.) Nitrites consistently 0.00 and Nitrates are around 5. Every now and then he will be fine for a few weeks and everything with grow back long and strong and then overnight he will have big chunks missing or large holes/slits developing. I have modified the tank so that his fins are unable to be sucked into the filter so I don't think it's that. I'm not sure if it's coincidence or not but lately he seems to have damage the day of or after a water change. I usually change 25% (sometimes 40%) but it's a quick process and he doesn't seem to get stressed out. I thought he might be fin biting but the slits and holes in the center of his fins don't make it seem that way to me but I'm no expert. He will have little ragged edges on other fins too so I don't know whats going on. The edges/regrowth look a little darker than the rest of his fins. I've tried Aquarium Salts, Kanaplex and Betta Revive baths previously but none have worked. He literally goes from fine to huge chunks missing overnight. What is going on? The only other thing I can think of that I've noticed is the PH test has shown a little darker than usual the last few times I've tested it. Please help! I get so overwhelmed, this has been going on for months and nothing helps! Thanks!