Welcome to TONMO James! While you are setting up, you can join my latest adventure with O. briareus
by following its
journal (there won't be much to post for awhile as this one is a month or less old).
There is a collection of detailed post grouped in the sticky,
Posts with Info for New Octo Keepers that should be helpful with more details (and answers to some questions you have yet to ask
) but I'll attempt some brief (if that is possible for me) opinions.
1. IMO - 65 gallon with 20 gallon (or more) sump recommended, 55 with 30 gallon sump doable - long vs tall or square.
2. Feeding schedule is not an agreed upon topic. Age and the individual octopus play into the feeding routine. I feed 6 days a week and fast (if the octo permits some come out and get anxious for their food and I don't deny them but may give a bit less) one day. Others feed two or three times a week. IMO the extra fast days works better for cold water animals. The amount varies with age and size. Our adults do well on one blue crab claw (with extension) daily or one frozen shrimp. The referenced post list gives more feeding information, including how to add variety from your grocery seafood counter (or Asian food store).
3. As with any aquarium, this varies depending on your set up. I have a solid preference for placing a filter sock with a large bag of carbon at the sump input as my chemical filtration. You will also need a skimmer (generally sized to twice your water volume but that depends a lot on brand). Skimmers are often a topic of need discussion but for an octo tank, they are a must to handle the ink. Weekly water changes and maintenance will be required.
4. O. briareus becomes too large to practically feed live food. When they are young, fiddler crabs (or any small live crab with claws disabled) are always accepted.
Paul Sachs is a wonderfully reliable supplier for fiddlers and I have been buying small full saltwater crabs from Kevin through his eBay,
At_Your_Door_Fishstore. Adult food can be most easily found at a good seafood store (Asian markets usually have the most variety).
5. Used aquariums can present a problem if they have ever treated fish with a copper medication. Getting a list of any medications used and then looking them up is what I recommend before considering a used glass tank. USUALLY a tank that was setup and maintained as a reef tank will not have this issue, will be drilled for a sump and should be excellent. The silicone used in glass tanks is a high potential for having absorbed copper and slowly leaching it back out into the water. Acrylics are not known for this problem. In all cases (new or used) you are likely going to have to fabricate a full top with lockable feeding/cleaning access.
