In short, I don't belive they eat every day like like fish do, or will.
More like snakes.
It's also plausible , it may be indicative that it's in a breeding cycle. I.e. Well fed. Ready to spawn.
Octopus need to eat everyday . You can skip a day maybe once a week. You need to feed to feed them alot and have very good filtration preferable a wet/dry filter with a very good skimmer. Temp is also a factor which is why you should try to find out where he came from or what kind he is so you can adjust temps accordingly. Most species dont live long up to a year at best. Good luck. Thanks Tom
From my research book marks.
A bit long winded but good
http://www.thecephalopodpage.org/octokeep.php
http://www.octopusworlds.com/atlantic-pygmy-octopus/
A very good and active resource (was anyway)
https://www.tonmo.com/pages/octopus-pet-checklist/
Adding. Be sure of it's species and make sure it's not a temperate (cold water) animal.