A little back ground. I have been keeping bettas for two years now. I was taking down a ten gallon tank and moved my beta from it to a 55 gal tank with other occupants being bosemani rainbows and a couple killifish and a common pleco. Anyway, I acclimated him this afternoon over a period of about 35 minutes. I left to take my son to dinner for his birthday and got home not too long ago to find my little guy had passed. He was in perfectly healthy condition when I acclimated him to the tank. When I found him his fins were completely shredded and he was deceased. Water parameters are perfect. Ammonia, nitrites, nitrates all 0, ph 7.6.
What would cause this? And in a matter of hours.
He was so beautiful. I'm gonna miss him.