Neither 70g or bigger is recommended for these creatures,
How long have you been with saltwater? the reason I asked how long you've been with salt water is because these octopus get big and if your not in it for the long hall avoid them , they are also classified as expert only , knowing how to handle these creatures is a must as they can latch on with a boa's strength and not let go and have a strong bite that is venom-is
octopus require a large tank lots of rocks extremely good filtration as they are very dirty eaters and need constant water movement, octopus require a tank with a tight lid that locks as they are the worlds best escape artists , all rocks need to be secured and they require low lighting
octopus can range in size they start out small and grow at a rapid rate, they start out around 2 inch and can get up to 4 ft in size some are known to get 16ft to 30 ft
When discovered, an octopus will release a cloud of black ink to obscure its attacker's view, giving it time to swim away. The ink even contains a substance that dulls a predator's sense of smell, making the fleeing octopus harder to track. Fast swimmers, they can jet forward by expelling water through their mantles. And their soft bodies can squeeze into impossibly small cracks and crevices where predators can't follow.
If all else fails, an octopus can lose an arm to escape a predator's grasp and regrow it later with no permanent damage. They also have beak like jaws that can deliver a nasty bite, and venomous saliva, used mainly for subduing prey.
Considered the most intelligent of all invertebrates, the common octopus is found in the tropical and temperate waters of the world’s oceans. They can grow to about 4.3 feet (1.3 meters) in length and weigh up to 22 pounds (10 kilograms), although averages are much smaller. They prey on crabs, crayfish, and mollusks, and will sometimes use their ink to disorient their victims before attacking. they require live foods 1lb grouper are the best feeders for these guys .
you need to remember these creatures are very expensive to feed , and get big fast