You might also try offering some thawed frozen shrimp (good quality). Most octos favorite foods are crabs and shrimp, but they also sometimes eat snails, clams, etc - depends on the species
I'm wondering about the heater - I've read that octopuses are insensitve to fire, maybe heat, too. I protect my octos from equipment in the acquarium by using loose netting (such as comes with the bags they sell for carbon or the type of netting that comes on aquarium nets). Since octos are so curious, it's a good idea to cover any water intakes. Some of them have even been know to take power heads apart.
Octos are very intelligent - depending somewhat on the species - can be playful. But they do need a tank to themselves, with maybe just a starfish or a pencil urchin as a companion. They need a cleanup crew, too, but some of them may disappear as food!
Nancy