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Smallest ceph tank possible?

jamest0o0

O. vulgaris
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Jan 22, 2008
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Okay so this wouldn't be for awhile, I'm more so just interested at this point and I'm considering cephs down the roads because of how awesome I've always found them to be. To start I've had a few years in reef experience already along with a decent amount of research on cephs in the past already.

My main question is what is the smallest ceph(being octopus or cuttlefish) that is commonly kept in the home aquarium? I would want to make it as simple as possible with the smallest tank possible(I don't have much room). I do understand cephs have special needs and require perfect water making good equipment and all a must. I have a PAR38 bulb as well, and this may be a stupid question, but are there red PAR38's that would support corals and at the same time allow nocturnal cephs to hide less?

Once again this is no short term project, I want to make sure to have everything right before doing anything.
 
Smallest envirionment is a good and common question and we are thinking about a way to consolidate some of the beginner FAQ's to provide consistent and extended answers for the new year.

The smallest octopus we commonly keep is the Caribbean O. mercatoris. It is a relatively inactive species, noctural and has short arms (a consideration when sizing a tank). IME, a 20 gallon tank with a HOB overflow skimmer/filter, edging around the top with a removable lid placed over the remaining opening and lowering the water roughly 1.5 to 2" with regular weekly water changes will work well for this animal. There lifespans are generally somewhat shorter than the larger animals. I have kept two males a full 13 months (tank born so I knew the age) but the females seem to live only about 8 (8-12 months is the generally listed lifespan). They are typically not very interactive and many keepers are disappointed when they keep them because they are seldom seen. A tank set up this way will accomodate two (but you cannot go smaller for one) if they are sibblings or found together in the wild (there may be other combinations but this has proven to work, if they are unknown to each other, then they should at least be the same size but the results have been mixed). Anything larger should be housed in a 50-65 gallon tank.

I do not keep cuttlefish but will pass on what has been generally recommended. The only cuttles we commonly see are S. bandensis. These are a small cuttle that grows between 4" and 6" adult size. They have done best when raised from egg (expensive live foods required the first month or so) and will need a smaller environment until they are eating well on frozen foods (generally at about 1.5" in length). Often, a breeder net is used until they can be freed to the larger environment. One can be kept in a 30 gallon tank but preferences have been to keep multiples and a minimum 55 gallon tank is recomended when housing 2-3 animals.

Keep in mind that both cephs live short lives and when you set up a tank you are designing it for different occupants each year. A 55+ (with sump if you heve the room) is a better choice for an on-going ceph tank. If you design it for octopuses, you can experiment with keeping both octos and cuttles over the life of the tank.

Cuttles can be tank bred and occasionly we have success with a couple of the large egg species of octopuses (O. mercatoris is large egged). Mercs will tank breed and we have several successes with multiple generations but larger octopus is problematic in that keeping them together often results in the loss of one of the octopuses. I have tried breeding a pair of tank raised (from a fertile WC mother) sibbling O. brieareus, giving supervised visitation (Roy breeds a number of different species in the Berkeley lab in a temporary pairing environment). The fertilization was successful but the hatchlings did not survive. Bendensis cuttles do much better together. There are still problems in smaller environments with fatal fighting but much less than with octopuses. (Note this requires a larger tank than the single occupant size mentioned) and will breed and lay eggs throughout their adult lives. The octopuses we commonly keep lay only one clutch of eggs and the female dies about the time of hatching (she will typically lay eggs, fertile or not, and die when the eggs would have hatched even if she has not mated).

I am not familiar wiht the red PAR38 lighting but note that the corals that can be kept with octopuses are limited to very low stinging varieties (like leathers, gorgonian, a very few polyps, sponges and mushrooms). Daytime lighting to support this limited set is fine but provide dim red light for night viewing. Cuttlefish are much more tollerant of corals (I'll let the keepers be more specific as to the kinds, the ones mentioned for octos are fine but I don't have the experience to list others) and have done well even under metal halide lighting as long as darker shaded areas created by your aquascaping are provided.
 
Thanks for all of the info. I wasn't too interested in getting a ton of corals, just whatever would be compatible with the octopus.

Would zoas and/or macro algaes be fine along with other softies? As for the mercatoris(not sure if I spelled that right) I know they are nocturnal, but do they hide at night as well or only when the lights are on?
 
Macro algae is fine, zoas are iffy as are most polyps. I recommend initally securing any polyp on its own rock before adding it to a ceph tank and then observe when the octo touches it. If you note a quick withdrawl of arms, remove the rock and put it in another tank or swap it. A tank environment is too small for stinging corals and octos don't go around things. The sting won't be fatal but can develop into an infection that can be.

I enjoy keeping mercs but don't have one at the moment. I find if you build out your tank with a collection of the the large purple barnacles placed about 1/3 of the way up the tank (usually easiest to secure it in the LR), most females will take it for a den and you will have an easy viewing. Males seem to change dens every couple of weeks and will use it but will also find other places. O. mercatoris can learn supper time and can be hand fed with either a feeding stick, pipette or your fingers if you are willing to work with them but they are quite noctural. If you darken the room around 9:00 PM daily you have a good chance of seeing them somewhere between 9:30 and 11:00. I leave the red light on over the tank 24/7 so there is no totally dark time in the tank and I think this helps to have them interact. I have had one female who would accept food at 6:00 PM even with the lights on but she was unusual. I never saw her leave her den though (seemingly characteristic of females that are fed daily).

My most interactive O. mercatoris was a tank born male named Sisturus. The link is to part of the journal I created for all the hatchlings but you can skim it for his name. He would come out promptly at 11:00 to eat even if the lights were on and would interact with me more than any other of the mercs I have kept. Sadly his tank mate turn out to be another male and he produced no offspring.
 

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