What was your ammonia at? What kind of octo and how big? His behavior could be related to senescence, though it could also be water quality related. Keep offering a variety of LIVE foods, once he starts eating you can try frozen. Offer the food with a feeding stick or with your hand and make sure your octopus sees it and recognizes it as food. I hope he makes it.
my nh3 level were between .50 and 1.0 ppm. i did a 15g water change last night and left 2 very small fiddler crabs in the tank.today i checked my nh3 level and they were fine.i also found the remains of the crabs scattered about the opening of his hole.so i think everything is ok,but i have not seen him yet tonight.