For your first two, the minimum recommended tank length is a 6 foot tank with 125 gallons---your third, applicable actually to either of the mimics, is recommended for a 4 foot tank with 75 gallons. Your 75 could support a tomini, mimic [either variety], brown, or kole. The kole is one of my own favorites---so solemn, and so very skittish, you think they're guilty of something, but they get quite friendly given time, and are rather colorful. The tomini is also a handsome fish.