• Looking to buy a cephalopod? Check out Tomh's Cephs Forum, and this post in particular shares important info about our policies as it relates to responsible ceph-keeping.

New tank setup with a pygmy octopus


Blue Ring
Dec 13, 2002
Although I have asked previous questions concerning a setup, due to certain budgetary restraints, I am forced to look for a new tank setup. I wish to know whether a 10 or 20 gallon tank OR LESS would be appropriate for a pygmy octopus. Also what is the CHEAPEST type of filtration and protein skimming that is possible for a tank of that size?

Thank you very much,
Michael O'Shea
What about one of those Eclipse 12 gallon setups? I'm using one as a freshwater feeder tank, with an eye toward eventually getting an even cheaper feeder tank setup and using this as a saltwater emergency/backup tank. Should be available for under $100...only thing it lacks is a skimmer, has integrated light, pump, filtration, biowheel. It's got a tight-fitting hood but aren't there some skimmers that are kind of "internal" that might fit within? Or could perhaps a lack of a skimmer be compensated for by a regularly changed bag of carbon? Of course...the price of carbon would outweigh a small, cheap skimmer's price fairly quick, so maybe fitting a skimmer is the better choice...

RE: Eclipse and joubini or mercatoris

Thank you very much for your advice...
If I were to use the 12 gallon Eclipse, would it possible to use a cheap IN-TANK skimmer, such as a Lee' Counter Current?
In addition, what sort of animals would be compatible with a joubini or mercatoris? (I.e starfish, flame scallops...)
And lastly, is your pygmy a mercatoris or joubini?
Mine is probably a c.f. bockii, per Colin's identification. I ordered mercatoris, but this is what I got... He may not be typical of the species, but he is EXCEEDINGLY timid. In over three months I've never seen him out moving. He moves around well enough and hunts, but he's strictly nocturnal and hides at the first sight of me (hence never catching him while he's out.) Mercatoris may be a bit friendlier.

If Pat (rudiger) comes back online he can tell you much more about mercatoris as he had a female with eggs.
Perhaps drop him a private message via the member's profiles?
Final tank setup

After weeks of research, I have finally decided on a setup recommended by a local fish store. The octopus he is willing to order is from the Caribbean, possibly Octopus briareus.
I will either use a 10 gallon tank with an aquaclear 150 and a Lee's in-tank protein skimmer, or a 20 gallon long tank with an Emperor 280 and a Lee's in-tank protein skimmer.
I have considered buying a pygmy online, but the briareus seems to be a larger and possibly more active species. My only concern is the damage it may cause to the in-tank protein skimmer.
Hello Michael,

Better look at your octo sizes again - the briareus has a body up to 12 cm (about 4 3/4 inches) and arms to at least 60 cm (about 23 1/2 inches). This seems quite large for a 10 or 20 gallon tank. Since you are on a budget and want the small tank, perhaps the best thing is to reconsider the pygmy octopus.


I have read that both O. Briareus, O. joubini, and O. mercatoris are all naturally nocturnal. What is the best method to acclimatize them to a "normal" schedule (i.e. active during the daylight). Or, if that isn't possible, what else can be done?

Michael O'Shea
Hi Michael,

My briareus never really got into the hang of being diurnal... She stayed pretty inactive through teh day but she had eggs only after a short time of having her.

From experience with other octopuses, all except the bocki i had got used to diurnal activity to a lesser or greater extent...

Being the 'food god' helps a lot!!!


I wished to know whether cycling a new sterile tank can be done with simply sterile aragonite and yellow damsels. If not, can lava rock be used in place of Live Rock? In addition, what is an appropirate number of yellot-tailed damsels or 3-spot dominoes for cycling?

Thank you,
Michael O'Shea
Absolutely...traditional cycling starts from "sterile." It's SLOW, but it works just fine. A handful or two of sand from an established tank at your LFS (many will do that for you for free or a buck) will help a bit.

Lava rock...um...will EVENTUALLY become colonized by bacteria the same way live rock is, but I haven't a clue how long that takes. Nor do I know what lava rock costs... Damsels are not friendly to octopuses, so you may want to look at a different fish...I'm not sure which is friendly though. One guy recommended clownfish.

I would just use black mollies that are acclimatised to salt water (takes about an hour or so) and they can be left in when octo arrives, unlike damsels. I would use about 10 or so of them.

Lava rock, like ANY surface in the aquarium will become colonised with bacteria to help in the nitrification cycle. It will never be 'live' rock with corraline algae etc but it will be home to bacteria.

It will take the same length of time that it takes for your tank to become properly matured which is exactly the same length as a piece of string!

Lava Rock

Thank you...
So roughly how many pounds of lava rock would be appropriate for a 20 gallon tank? Also, I have read about dead spots when stacking rock. Would the stacking of lava rock create such conditions?

Thank you,
Michael O'Shea
Well that is entirely up to you how much rock you put in. Its more of a matter of taste than anything else but for an octopus the more the better.
Teh more hiding places you add the quicker it will relax, feel safe and wander from its den.

Yes, you can get dead spots but that was more of a problem with deep sand beds and undergravel filters. Just dont make teh gravel thicker than about 1" or so and position powerheads to make sure that they circulate the water all about the tanks... Some careful planning while adding the rocks will be effective

lava rock

instead of using lava rock, you might want to mail order in some live rock or pick up base rock from your local store...lava rock can be VERY tricky in a saltwater tank...those small pits often contain large amounts of metals which will disintegrate in the tank and kill everything. base rock from your local supplier has been pressure washed to remove all that stuff!

Shop Amazon

Shop Amazon
Shop Amazon; support TONMO!
Shop Amazon
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.