I collect marine specimens for research and education in the North Florida Gulf Coast. For a small easy to keep Octo we supply Dwarf octopus,( Octopus joubini ), they are active at night and inhabit empty mollusk shells. We feed them small crabs such as Dwarf Hermit Crabs ( Pagurus longicarpus ). I have 6 in a ten gallon setup, but at our lab with flow through from a 50,000 gal. system. Filtration and water quality here are very stable. However I have keep them at home in a twenty gallon setup. I have never lost any from climbing out of the tank but researchers have reported theirs jumping ship usualy from water quality problems. They live for approx 6 months and are well worth a try. We cannot supply to the pet trade but someone in the forum may Know a collector on the northern Gulf who could supply these.