As stated above, they need Olympic size swimming pools to be comfy. I don't think they should even be sold in LFSs. BUT, in an effort to pass on a tidbit of actual info.... (if u haven't experienced this before, it will throw u for a loop) When stressed from a water change, a harassing tankmate, a large meal, or other things u would not necessarily think would freak them out too bad, a RTC will shed its slime coat layer into the water. It looks like a giant bogey gliding thru the tank. I have read that they are supposed to be more susceptible to disease right after this happens, but the one I had never had issues. It is a freaky thing to witness. Maybe this happens with other cats, and u have seen it, but if u haven't, be prepared. It doesn't take a whole lot to get them to shed it.
I made the mistake of buying one of these for my 240 when I first got it years ago. I was still a novice, and (OBVIOUSLY) didn't know what I was doing. I actually found a LFS with a large display tank to take him, but even that would not have held a full grown specimen. Don't know what happened to him in the end. Even tho he was one of the coolest fish I have ever owned, it was a mistake to buy it, and I think it is a mistake to sell them. IF u really have a LARGE heated pond, go for it. They become hand tame and are exceptional fish.