I've had alot of recent deaths. Tank has been setup for about 4 months, it is fully cycled using ammonia method. Water changes are 50% every week in increments of 25%. Parameters are: Ammonia: 0 Nitrite:0 Nitrate:0.25 Ph:7.4* Gh/Kh: not known Stocking: 4 harliquin rasboras 2 albino corydoras 2 peppered corydoras Deaths: 4 harliquin rasboras 3 albino corydoras 4 peppered corydoras Rough timeline of deaths: 2 fish one week after I added the new fish 2 the week after 3 early the next week 1 2 weeks later 1 2 weeks after that And 1 a few days ago Everything was going fine for about 2 months, then I added non quarantined fish (bad I know, but damage is already done, will quarantine in future). One of these fish had half it's tail missing and some of the other corydoras started loosing their tails too so I treated for fin rot (melafix) it did nothing at all. The rasboras and some corydoras died with no fins missing and no obvious sign of other disease. The fins on the corydoras weren't bad to the point of them dying of that. Every fish that has died has been acting odd, heavy breathing, rapid swimming then died within 24hours of that except 1 (who I cloved) that was on the bottom of tank emaciated and his spine all twisted he was acting wierd for 3 days before he went to the bottom and his spine twisted in about 3 hours I cloved him after that. I had another tank (fully cycled with same parameters) with a veil tail betta. I made sure not to cross contaminate anything between tanks he also started loosing fins and then within 3 days was dead (he had clamped fins when I got him which appeared to be getting better with the warm water. He had been in that tank for about 2 weeks. I'm thinking water just because of the same kind of death in my betta tank and the medication not working and not all fish being affected at this point. I have added carbon to the tank to try to filter out anything I could I've had 1 death since then. I have no way of using any other water as I am in the middle of nowhere. If you have any ideas at all on what it could be please let me know, ive been toying with the idea of it being columnaris.