I was wondering what I can do to get my fish that have/had fin rot to grow back their fins? Details: I have two tanks, a 20 gallon and a 30 gallon. The 20 gallon has two cory catfish, 2 cardinal tetras with major fin rot issues, and 3 pristella tetras. The 30 gallon has 4 zebra danios, 1 cory cat with major fin rot issues, and 3 some-kind-of tetras the female of which has some tail fin issues. Both tanks have bubblers and filtration. Both tanks always test perfect on all water parameters (ie. no ammonia, or nitrite), nitrate is low. I have hard water; there is ammonia in my local tap water supply so the conditioner I use removes everything. The tanks have water changes every week of 15-20% and gravel suctioning once a month (but there's never much crud down there). I don't have algae issues in either tank. Why are the fins not regrowing? 
Thanks!
Thanks!
