Our octopus is a Bimac, and he's in a 40 gallon tank. We have a protein skimmer and overflow that goes to a 20 gallon refrugium. The Bimac (Octopus bimaculoides) is actually diurnal so he runs around the tank durning the day. We feed him guppies which are freshwater, but they from our own guppy colony. I'll get a video up tomorrow of feeding him a fish with the tongs. This is the second octopus, the first one never did really move, we think it got really stressed during shipping. This one was chasing around hermit crabs in the styrofoam box he came in while acclimating. The tanks has mess all around the overflow boxes and the return tubes (i dont know what to call them), so there really isnt much way he can get out. Also, this guy doesnt really seem to try to get out. he mostly just looks for food.