Tank sizes of RTCs are often discussed here.
A healthy adult RTC in captivity will bee around 4 feet or possibly even bigger, so it would make a 8 feet pool look small.
The RTCs i have seen at public aquaria where all very active, and have heard the same from others that have kept large RTC's.
I remember once someone posted a thread on General Aquaria Discussion, about a guy on craigslist that had a Red Devil, or Texas Cichlid in a round tank that was about twice the lenght of the fish, and people where very angry at that guy, som even threadened him if i remember correctly, or said he derseved to be beaten or something. I dont get why its acceptable to keep an RTC in a pond/tank thats twice the width of the fish, but not a Red Devil, Texas Cichlid. The activity level difference cant be that big.