So it's long arms and small. That's about all I know so far. It's small enough to fit between every rock in my tank (making all my caving irrelevant). The real interesting part is that I made my caving and rock base out of PVC. It has a large doube opening that hooks to the stand up 3/4" pipe. He goes into the double cave and into the hole in the pipe, all the way to the top and out of the rock work on the other end. So he lives at either end of a piece of PVC currently. He ate some shrimp from a stick last night!
So today it took a piece of shrimp from me all the way back through its tunnel and left the shrimp outside the other end. Is he saving it for later or discarding it? Do I need to find a new food source?
When they are first introduced to an aquarium we have seen octopuses exhibit either gluttonous consumption or stubborn refusal. I recommend continuing to offer food every day and remove anything not eaten after a couple of hours. Initially, size seems to be important and I have found that starting with small pieces (about the size of the eye) seems to work better than offering a single large portion. Once the food is accepted and eaten, I increase the size until there are left overs. Quantity consumed will change over the life of the animal with young animals eating more as they grow into adults and older octos slowly consuming less. It also seems best to develop a diversity of accepted food and alternate during the week as the larger (ie not dwarf) octos I have kept appear to get "bored" of the same food every day.
I would suggest removing the shell before feeding. There is no nutritional value (octopuses don't eat it), it is hard to be sure you remove all of it, and it will quickly degrade and add ammonia to the tank. I do leave the shells on the crab claws I feed but claw shells are easier to find and the meat much harder to extract in one piece.
So he takes but rejects thawed shrimp. I have a bunch of small hermit crabs and a small blue crab in the tank. As well as 2 clowns, a lawnmower blenny, and a leopard wrasse. I am going to try fresh shucked oyster tonight. And I'm trying to find fiddlers today. He won't starve right? Also he has moved to the cave/den behind pride rock and that's super exciting.