I never tried octopus, but I feed my Gars squid regularly. They accept it, but it is my impression that they are not as fond of it as they are of fresh market fish.
As gross as it may sound, it seems like most all of my fish totally berserk out when given fish organ meat. It makes it easy for me since there is a world famous market (Lexington market) with numerous fish vendors with its own light-rail and subway stops that I transfer every day coming home from work.
To date fresh fish that I have fed include (Graded on a scale of 1 [worst] to 10 [best] based on factors including appeal to fish, filleting ease, cost and water fouling:
Tilapia - 5 (Very thick skull, heavy bones and sharp fins make it a tough cut, waste)
Spot - 8 (Extremely easy cut & a top appeal, very little waste but clouds water fast)
Croaker - 4 (Skull so thick you practically need a chainsaw to get at the brain, heavy bones, sharp finage, lots of waste)
Bass - 6 (Excellent feed other then being pricey)
Perch - 10 (perfect feed well liked, easy cut, little waste and not too messy!)
Grouper - 5 (I had the market cut fillets (for family), very bland so became fish feed)
Porgy - 8 (Easy but some sharp bone & fins need removal)
Butterfish - 9 (easy & very little waste)
Trout - 10 (perfect feed)
Mullet - 6 (extremely messy and can gag a maggot/ knock a buzzard off a meat wagon)
Flounder - 3 (Way too expensive for fish food!)
Thawed frozen and already cut varieties):
Pollack
Haddock
Swai (Not well accepted!)
Catfish (Messy and not very well accepted)
Silverside Minnows
Steakfish/ whitefish ...