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Keeping an octopus(bimaculoides) in a 55g (newbie)


Pygmy Octopus
May 19, 2004
I have had a 55g reef tank now for about a year (with success) and would now like to try something differrent. Im willing to break my tank down and get rid of my fish, corals, anenomes, and etc. to go the octopi route. In my tank I have about 75pds of live rock and about a 1and a half in. sand bed of argonite and bits of crush coral. I am running a canister filter, the Fluval 404 with activated carbon and bio-max. I have an Aqua C Remora protein skimmer with two maxijet 295 gph power heads. Also i have a 265w Custom Sea Life PC fixture(2 10k bulbs and 2 true actinic) with moon lighting.

Now for the questions/concerns

I would like to keep a bimac in my tank but the depth of my 55 is pretty narrow (13.5 in) is this ok, especially with 75 pds of live rock? Should I make more of a rubble zone with my rock or higher archs for caves? I will be removing the crushed coral that I have left and lowering the temperature to 72 dg F. Should I keep my pc fixture and convert the bulbs to 20,000k bulbs or put on the old strip flourescent fixture? Can I keep my sand sifter star and brittle star?

Am I forgetting anything? How does my setup sound? Anything more I should be aware of or know? Also how big do the bimacs actually get?
Thanks for any help,
Patrick :?: :shock:
Hi Patrick and welcome to TONMO.com :welcome:

What are the other dimensions of your tank? - I'm assuming it's a long tank. A 55 gallon is large enough for a bimac. Our adult bimacs have varied in size, with a mantle length of maybe 5 to 8 inches. A few got quite large.

You don't need much light for an octopus - one 30W fluorescent bulb should be fine.

That's probably too much live rock for an octo tank - one pound per gallon might be better - stack the rocks up in a secure way, providing caves and openings for your octo. (Octopuses are very strong and will eventually redecorate your tank.) Allow a free area of sand for play and hunting.

How large is your starfish and brittle star?

That's a start on answering your questions!

Hi Patrick, wish i'd seen you posted here before i replied on reef central :wink:
the sand sifter star is about 3.5 in and the brittle star is huge probaly 12in across, his head is probably near the size of a half dollar. I dont think I will be able to keep him especially with a youger bimac. Couple questions. How much flow is recomended for these octos?Im gussing you need lots because more water movement means more oxygen right? I think I have plenty with my fluval 404, protein skimmer, and two maxijet 1700's.

dimensions are 48x12.5x22.5
Hi xyzner,

Yes, it's a good idea to set up a feeder tank, but it will probably be more for baby clams and crabs at first. Small octos have a hard time catching shrimp, but they learn that later. Even the small octos will usually accept small pieces of raw frozen shrimp (thawed, of course).

Very young octopuses can be fed more than once a day - offer a few baby clams or a little hermit crab and, when that's gone, offer a bit more, maybe a tiny piece of shrimp. You'll figure out how much it eats and what it prefers. I'd imagine you'd put (or already have) amphipods in the octo tank. I think you'd benefit from reading over the past posts in Journals and Photos, where people describe feeding their newly-acquired octos.

I'm a little worried about my pod population due to my sand sifter star. I think when I sell my fish i'll go ahead and order the pod farm from octopets along with the clams and bimac. What about the star and brittle?.....do they stay or go?
Your brittle star is huge compared to the size of a baby octo and might steal his food. I would find a new home for him. I've never had a sand-sifting star - don't know about this one. But if he's eating up your amphipods, maybe he should go, too.

You also asked about flow - an octopus doesn't need a huge flow, but plenty of oxygen. Many of use a wet/dry (trickle) filter, protein skimmer and powerhead. Some people add a bubbler, but the octo will probably play with that (well, they play with the powerheads too, sometimes!).

Yes, increase you pod population - good idea.

Alright, looks like i'll be clearin' out the tank! lol........should I leave the snails and hermits that are all ready in the tank and let the octo go ahead and snack on them whenever? Also what kind of echnoderms do you reccomend? mini serpant stars?

inverts i'm going to leave in the tank (probably):
1 emerald crab (pretty small)
about 7 astrea snails
near 50 nassarius snails (probably 40ish)
1 giant mexican turbo (I think)
assorted hermits
whole bunch of smaller hitchhiker snails (smaller than the nassarius)
sound good???/ :?
Oops, overlooked this posting - that's why I'm late!

Snails are fine. Crabs are fine as long as they're quite small - but some of the ocots people are getting are so very small, you'll just have to see.
Some people prefer to hold the crabs in a second tank, so you can put them in one or two at a time and you know exactly how much your octo is eating.

An urchin (non-sticky) is fine. How big is a mini serpent star? You might see how they get along, some will take the octos food, and some octos will take the serpent star's food.

ok.........I have some questions about certain inverts, are sea cucumbers ok? what about nudibranches, anybody ever try these? I think I am just going to keep my brittle star and sand sifter. The brittle star would not eat an octopus right? Also on my reef, I am just using tap water but we have a soft water unit. I should not worry about copper in the water as long as my corals and shrimp and other invertabrates have been doing fine for the past year right? My fluval 404 is constantly running activated carbon and this removes heavy metals so I guess I am fine for sure???

Are there any certain ways I should setup the live rock? I know that they need a rock free area for playing and hunting but when making the caves, should I make it small, or a large open cave where you can see inside it? (im going to have to look at the members photos for an idea! :biggrin2: )
Just thinking about another thing after reading.......... do bimacs tend to bite people? and do they have a certain type of venom? also I am having a difficult time finding pics of aquascaping.....
Hi xyzner,

I'll answer your last question first. Yes, bimacs do sometimes bite their owners, either out of curiosity when they're young, or by mistake.

If you will go to Journals and Photos, in May you'll find a video of Inket biting Carol's daughter while being fed (and he seems to feel bad about it!) - also look at The Agent Bites.

The bite is not bad, something like a bee sting.

You're right, forget sea cucumbers and nudibranches.

I would definately test your water for copper. Octopuses are very sensitive to any copper.

A lot of people have posted tank photos - if you're patient and look back through the past postings, you'll find a lot. Yes, we usually leave some open area. Your octopus will grow, so you need to leave large and small caves. Make sure your set up with the rocks is sturdy, since even a small octopus is very strong and can move rocks.

Hope that helps!

Ok, what about chocolate chip starfish and a blue tuxedo urchin? I think this is what im going with? Also I have these tiny snails in my tank and there are lots of them. Do you think a baby octo would eat these? They're about the size of 1/2 nassarius snail. :!: :?:

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