Originally Posted by OrangeAugust
It takes a 5 gallon tank a loooooong time to heat up to the temp you set your heater at- like at least a few hours. So I don't think that could have shocked him.
I disagree on this. Temp fluctiations of 6 degrees are stressful even if it takes a few hours. Personally, I wouldn't raise it more than 1 degree per hour, or more than 3-4 degrees in 24 hours. How exactly did you acclimate him to the new tank?
It is possible that he was sick in the store when you bought him, but I'm thinking this was some kind of shock. If you got him from a nearby store, their tap water parameters are likely close to yours, but since you aren't using tap water, there could have been a major change in pH. I wouldn't be surprised if it is a mixture of temp and parameter fluctuations, as clamped fins are often caused by stress from shock.
I would also give him plenty of time to warm up to the new tank and make sure it is decorated well enough. Maybe keep his tank dark or very dim and give him space and time. Hopefully, if it is shock, he will start to improve with time, and no negative side effects come from the stress... He was also likely very stressed in his cup when he was purchased.
When I purchase a new fish, the cups are generally pretty dirty and I want to get them out of the old water as soon as possible, but most of the time, not acclimating slow enough is worse than them having to spend a little extra time in the cups. When I got my male CT he went on a 2 hour drive home and I left him in his cup undisturbed for about 2 hours after I got him home because he was still shaken up from the car ride.. I also avoided putting him in direct lighting, and after those couple hours he calmed down quite a bit and THEN I started slowly acclimating him.