I need some help. I have three tanks, 10, 28, and 38 gallon (all well established, 1-3 years). They have all been doing very well for some time now. Out of the blue, fin rot pops onto my guppies in the 10g and my corys in the 28... Same time! No biggy, went for the triple sulfa (my idea), then Kanaplex... Then erythromycin, then pack to Kanaplex (following directions and water changes schedules and advice from fish store man). The guppies continue to have symptoms (it's been maybe a month of treating). Meanwhile, I've of course been doing weekly water changes. The water quality in all three tank remains flawless upon testing (only a minor ammonia spike once in the 38, cleared in a day). I'm pretty sure the corys never lost the rot either... And, now the largest cory has a giant swelling under his chin, making a kissy face almost. Prazipro was recommended, which I have administered twice in three weeks to no affect (none of my tanks have carbon in case you were wondering). Now, the 28 gallon is going berserk! Cory with missing whiskers and fins, a black phantom headstanding very slightly, a gold barb doing the irritated twitch and rock scrape, and an otocynclus with scarlet red belly and mouth to top it all off. I turn to my 38 and smile with satisfaction... But wait, what's that red abrasion on that gourami, and did tetra just do the rock scrape dance? I am struggling not to type the curses that are rolling through my brain! Sooooo frustrated. Please help before I end up spending hundreds of dollars on meds and losing all my fish anyway. :-( I have had this problem with almost all of my fish that have gotten sick in the past year, no meds cure them.