A 30 is fine for a dwarf species. The divider, possibly not. Some dwarfs do well together. We have success with O. mercatoris (Caribbean) that have been living in close proximity or are siblings. The lesser Pacific Octopus , also a dwarf (O. chierchiae -- very rare) is known to live similarly. However, trying this may cost you one or both of them if they turn out to be aggressive or cannibalistic. If you use a divider, I would recommend using something opaque with holes no larger than their eyes (the beak is the actual restriction but beak and eye size are roughly the same). If they can detect each other and are mixed sexes, aggressive or cannibalistic problems with ensue. It might be better to use a clear divider and put live food on the other side.