Ditto on getting the tank to full maturity before even thinking of getting a Cephalopod of any sort. These are Expert care creatures and not meant to be housed in just any tank. I haven't seen anyone ask yet... Do you have any experience with keeping full blown saltwater reef tanks? Have you given any consideration to cuddlefish? Easier to care for and maintain than the eight legged ocotpus.
1. Tank lid must be able to be clamped shut. Octopus can and will lift any screen lid off that is not clamped shut or weighted down some how.
2. Mature tanks need only apply.
3. You will need to find a way to keep the live rock in the tank form being moved around by the octopus. Glue the rocks down or what ever needs to be done to keep the rocks in place.
4. Are you ready to and can afford to spend the money on feeder fish and shrimp? Do you have sources for these?
With all that in mind. I would recommend research as much as possible before purchasing. Get the tank set up as if it will be a full blown reef tank, as you will need most if not all the reef tank stuff for the octopus. Give your tank a chance to mature and go through a full cycle.
Oh yes, and having an octopus wrap around your hand and arm is a whole lot different than that of a snake wraping around your hand. Eight legs and a whole lot of sucktion going on there.
Cheers,
Alex