I'm setting up my 90 gallon saltwater tank next week and i was thinking about keeping an octopus in there, I want a WOW factor in my tank and people will definitely be amazed by an octopus. What is the life expectancy of an octopus and is 90 gallons a good size?
90 is a very nice size for most of the species we keep (only one needs more room). Their natural lifespan is only about one year and we don't get them at birth. The tank needs to be a species only tank so you can keep a few interesting clean up crew animals but no fish or decorative crabs. There are a few softies you can add for color but nothing with a strong sting.
Not all octopuses will cooperate with your wow desire though as they are naturally shy animals and sleep a good part of the day.
If you would like more corals, you might consider cuttlefish. Longevity is about the same but there is a good chance they will breed and you will likely start with eggs so you will have the full time with them. They are labor intensive and expensive to feed for the first two months though.