I have a 3 gallon I bought from a thrift store about a month ago and I had put my HM Betta, Roy, in there to give him a bit more room. He was always really sickly and was showing the early stages of Dropsy at the time, but I think the change in tank stressed him too much and the disease killed him. (R.I.P)
I'm not entirely sure, but the 3gallon may have also contributed to his death. I had cleaned it with boiling water, white vinegar, and baking soda and let it sit for about three hours before dumping it and scrubbing the crap out of everything. Then I sealed cracks in the tank and, overall, it remained unused for about a week before I added my (already sick) fish. But I still think, even after cleaning it, there might have been something in there that got to him. :(
It's been about two weeks since he's passed and I want to try and re-use the tank now, but I don't want the new fish to get sick like Roy had been.. so I want to know how to REALLY clean the tank and all of the accessories.