It is not uncommon for them to be shy when they are first put in a tank. If it is a dwarf species then they are nocturnal and very sensitive to light. What do you abut it? Do you know what kind of octopus it is? Where it's from? do you have Pictures? sorry to ask so many question but the more information we have the easier it is to help you.
I'm excited for you and anxious to hear more about your new buddy.
I call the first two weeks, "hold your breath time". Octopuses are very shy and even a diurnal will hide for awhile when first introduced to the aquarium.
How and what are you trying to feed? Putting small, live crabs in the tank for it to find is a good way to start. Fiddlers seem to be the most universally accepted, some will eat hermits (at least initially and I have recently discovered removing them from the shell makes them more appealing once the octo will take food from you).
If you ordered it on-line, provide the name of the supplier as well (posting of the listing is helpful, and allowed). If it was from an LFS, see if they will look on the invoice to see if they can determine its origination.
Thanks for responding. It is a Pacific Brown Octopus from a reputable LFS. I put in pcs. of raw shrimp, but couldn't put near Octopus because couldn't find him. He hasn't eaten any yet. Just got some very small hermit crabs. I think I spotted him in one of the live rock holes today. How long can they go without eating?
Unfortunately, that description is just about the same as saying it is an octopus. Where are you located? If we assume this is an imported animal even the "Pacific" is likely not correct/or not helpful. Most Pacific animals need cold water but without knowing the species, keeping the tank close to 72 and no hotter than 75 is wise.
We can start with a basic description but you are unlikely to remember without photos. A few things to look for when you do see it is recording the mantle (the part behind the eyes to the tip of the body - the bag like structure) length, and the proportional arm length (arms are how many times the size of the mantle). Look for mostly consistent markings (several species have ocellus (false eyespots) below the eyes at the base of the arms). See if it shows small bumps on the skin sometimes and then not at others. Look for little "horns" to pop up on the top of the eye stalks.
They can go several days without eating but young ones need to eat more often than older octos. Don't leave dead shrimp in more than a few hours. They won't eat it after that and it will start breaking down in the tank. Ammonia is a major no-no.
To help you care for the animal we also need to know something about your tank. Size, configuration and octoproofing.
well i called the pet store and the owner said he didn't know, just that they're shipped in as "brown octopus". sorry i don't have more info about that. my tank is a 40 gallon with an emporer 400 filter. I have the entire top of the tank covered with a screen with only a hole that fits tightly around the intake tube. the body of the octopus is about the size of the big grapes. no horns on the eyes or bumps on the skin. thanks for the help.
P.S. I think he's eating the hermit crabs that i started putting into the tank so i'm pretty sure he's okay.