4ft is perfect and they love driftwood and caves, temps for most Bullhead are good between 45 and 80 degrees as long as it is done gradually, Zimmermans fish, Jonahs aquarium, Btdarters and Sachs aquaculture are all highly rated native lfs's two of which I have purchased from; You would want adult sunfish with adult Bullhead, or young sunfish with young bullhead otherwise one will usually become lunch. You could put two Bullheads I with 4 large Lepomis (Bluegill, Green, Pumpkinseeds, Redbreast, Warmouth)or 6 medium Lepomis (Spotted or Central Longear) in a 120 with no problem.