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A few ?'s on tank and ID.


Apr 29, 2007
Hello everyone!

I'm new here and before I ask my questions I thought it might be helpful if I told you just a bit about myself. I've been keeping freshwater fish for 9 years now and saltwater fish/reefs for 7 years. Right now my only salt tank is a FOWLR (also have 4 FW tanks) but I have been interested in having an octopus for many years, just never had the opportunity (as far as tanks go). So at the moment I have a 40g tall tank which is okay as far as gallonage if I'm not mistaken, but what about the length of the tank? Too short? (36" btw). My main question is about ID'ing the octo you buy. After reading some of the articles I understand that a positive ID can be tricky. I want to keep a bimac so how do I tell for sure that it's a bimac I'm getting?? Where do you guys and gals get your bimacs from??
Thanks for any and all help! :smile:


TONMO Supporter
Staff member
Mar 8, 2004

The 40's a bit small on the volume side, the recommended minimum is 55gal for a bimac. A large sump might help there in terms of water volume. As far as the shape goes, Nancy has mentioned that there have been issues with octos jetting and bumping into the glass sometimes... this is a notorious problem with cuttles and squids, but some octos have trouble in narrow tanks as well.

You're right that species are often misidentified in stores, particularly when wild-caught. The best way to be sure of getting a bimac of known age is to buy one that's been tank raised... there are now two people working on tank breeding projects, Zyan Silver and marinebio_guy -- watch the "Octopus Availability" thread for more details.

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