Many of the dwarf species look a lot alike in that they are reddish brown (with little other color options other than white, nocturnal and do not show much/any dimensionality in skin display. The arms are really too long for O. mercatoris but there is another Atlantic/Gulf species (Octopus joubini) that has been confused with O. mercatoris for years (at least 50) and I have not been able to find definitive picture pictures to feel comfortable with how to tell the difference. One telling factor is the egg size and quantity. mercs are a large egg species where joubini lays small eggs but that does not help with visual ID. The fact that this was labeled "Pacific" would eliminate either IF the origination identifier is correct (often it is not).
Little update on my boy Clyde. He waits until all the lights in the house are off and comes out almost instantly. Last night I saw him in the PVC pipe and he was blending in. He was all white! I took a picture and then he went to his normal color though.
I also attached a small video of him climbing along the glass. he's a big boy!
So I got Clyde a bristle star fish. A tiger one to b exact. I notice this star to mostly hang out in a rock but tonight I saw Clyde kill a crab and take it under s rock. I got a little later and saw the star fish and had it whole and it blew me away. I thought maybe Clyde just killed it and didn't want it. But on my way back through I saw Clyde and the starfish fighting over the crab!
Literally arms were flying everywhere over this crab!
Should I remove this star fish?
Edit: crab is on sandbed now, and to me it looks like Clyde is trying to go after the star fish now. He's mad. Lol
They should be fine together and the star will help keep the waste minimized but you might try offering it a small piece of shrimp or other meat when you feed Clyde to be sure the star is getting enough to eat as it can't win a tug of war with an octopus. Some brittles will learn feeding time and can be hand fed, however, I am not sure how difficult this might be with a vulgaris in the tank.