I have a RTC in a 90 gallon tank. he was in a 55 before, and i know he will outgrow the 90. i do not want to buy a huge tank, so i was thinking it would be best to keep him in a swimming pool or giant tub when the time comes. my question is, how are these setups kept? how would i heat the water of swimming pool? what would be the best way to filter it? sump tank? I live in the northeast so i have to make sure the water can be heated properly because it can get very cold.