Mine is tupperware. I dont buy huge colonies though. No heater or powerhead. Never had problems with that setup so never changed it. Remember that most corals are alot less sensitive to temp swings than fish. Alot of corals on the reef are even in the air during low tide.

If I do buy a large colony I have a 5 gallon bucket that is used and marked with sharpie so it doesnt get used for water changes.