Cuttlefish, I have kept these amazing animals for quite some time. So from my experience here we go Not for beginner's, keep in reef, or alone, water parameters need to be top notch. (I use water from the atlantic ocean). High oxygen content. Just be aware the ones I just received were tiny. Size of a small pea. They are in a plastic holding tank inside one of my mail tanks. Feed brine and mysis shrimp. Growing nicely. Adult can and will kill tank mates these are amazing animals.