So I rescued three small goldfish (2 inches long) from someone who was losing her house. I set them up in my 75 gallon aquarium on sunday January 4th. Yes freshly set up, with decorations, gravel and 5 gallons of water from their previous tank. Monday night I was looking in the tank and didn't see one of them. so I moved a log and he was just hanging out under it. this sent up red flags and I decided to do a water change (i didn't have any test kits). did the water change and hoped that would suffice. The next day, same thing, just hanging out on the bottom. I went and bought an ammonia test kit (that was the only one they had) and some ammonia remover JIC. I honestly couldn't tell if the test was reading 0ppm or .25ppm so I did a water change and added ammonia remover JIC. the next day he looked worse. Today before I left for work he was struggling near the top. I'm sure I'll get home and find him dead, but the other two have been fine. I'm at a loss. I mean I know this isn't an ideal way to go about it, but the other two seem fine and I am doing water changes. could it really be issues from cycling this soon in this big a tank?