Octopus Mercatoris, from Florida coast. Only get about 3 inches long. That looks like a juvenile, so you might have a few months worth of life out of it. You can look at Cephbase.org and find more info, or TONMO.com. One member there is raising babies.
They don't ink much at all. Not enough to worry about. Any skimmer would take care of ink anyway, it would NOT be a threat to your tank if you have a skimmer running. Throw in a Fiddler Crab. It's fun to watch a tiny octopus take down a Fiddler the same size, will blow your mind how tough they are.