Have you done any research on either of these?
Before you buy a cuttlefish...
The drawbacks with Sepia officinalis...
They get big! You are looking at an animal with the potential of about 45cm (18") An aquarium of about 200 gallons is needed.
It can be very expensive to buy all the necessary equipment. They need large tanks with large filters and large protein skimmers!
Its not just one tank either! You will probably have to set up another tank with necessary equipment for keeping their food alive too.
Live food is a necessity, especially when they are young. Even when large it should make up the bulk of their diet.
They need space to swim and move about. A lot of their time is spent hovering at the front glass watching you; typical reef tanks are not suitable.
They are not a tropical species; tropical temperatures make them more skittish and can greatly decrease life expectancy.
If they get a fright and jet off backwards into a rock or the side of an aquarium they will damage themselves! It's called 'butt burn' and basically involves the cuttlebone being exposed right through their back end! Nasty! Lots of space and no sudden frights will prevent this.
If they get a fright and ink; a large individual will eject so much ink that you cant see one inch into the tank, hence the large skimmer is needed with plenty carbon.
They eat a lot of food. An individual that is half grown will eat two 5cm (2") wide crabs per day and more on top of that. 12mm long babies can and will eat up to five 12mm (1/2") long shrimps each day. This also necessitates the big filters, skimmers and suitable clean up crew.
It can be very expensive to source and provide a suitable diet. They eat a lot of shrimps and crabs. Fresh is preferred over frozen and live fish (goldfish) is not a suitable substitute.
If you keep several together you'll obviously need an even bigger tank. They
will fight over food and occasionally spook each other; it is quite common to see bite marks and two cuttlefish normally end a minor dispute by spraying ink everywhere! (Note this can also include the wall behind your tank!!!)
Baby
S. officinalis will not accept dead food until they are about 5 - 7.5cm long (2-3")
Just like an octopus, don't try and keep a cuttlefish with fish, shrimps or other similar animals. Some animals you can include in a cuttlefish tank are hermits, brittlestars and possibly some polyps.
Cannibalism can be a possibility. Don't feed squid if you are keeping several together as cuttlefish seems to taste like squid to another cuttlefish! It can encourage them to 'taste' each other. Often with disastrous consequences.
They can spit water out the top of their tank by using their siphon. Worth considering where you keep all your associated electrical equipment.
So why should you NOT buy a blue-ringed octopus? - The Cephalopod Page
THESE ANIMALS CAN KILL YOU! And more importantly, even if you are knowledgeable of the risk and take all the necessary precautions, if they don't kill you, they could kill your daughter, grandson, or the neighbor kid down the street. Inquiring hands get into tanks, and octopuses get out of tanks. An octopus will push through the smallest crack to escape, so a typical aquarium canopy will not contain them. Even with "escape-proof" tanks that we have designed specifically for small octopus, they can and do get out. A major concern in our laboratory is that a blue-ring will escape onto the floor and someone unfamiliar with the danger will take pity on it and pick it up using bare hands. Another risk stems from the fact that a blue-ring will crawl into the tiniest nook or cranny in a tank and remain there for days. More than once, even after the most thorough search, I have concluded that an animal had escaped, only to have it reappear, sometimes in my hands, while I was breaking down the tank.
There is too great a risk of someone dying to warrant keeping these animals just so you can have the prettiest, most deadly octopus on the block. I was lucky once and avoided tragedy at the arms of a blue-ringed octopus. Please learn from my experience and pass on buying one next time you see a blue-ringed octopus for sale.
