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Tank question...


Larval Mass
Sep 5, 2005
Ok, I have a few questions here. I am wanting to get a bimac but am wondering if it's ok to keep them in a smaller aquarium, 20 gallons, while they are small. It seems like a 75+ gallon aquarium with LR would make it quite hard to find something with a 3/4" mantle. I know some people put smaller containers inside of larger tanks but already have a 20 gallon set up. How long would a bimac 3/4"-1" last in a 20 before I would need to move it into a large aquarium?

Also, does anyone have any actual facts on how bimacs go with soft corals like zoo's, rics, etc? I have heard no, and I have heard it's ok and am not sure what to think.


TONMO Supporter
Nov 14, 2002
Hi Squier,

I dont think there is anything wrong with growing a baby in a 20 ubtil it is a bit bigger. I have done it myself and moved them onto a bigger tank once large enough.

A 20 might do a bimac for a couple months.

Just be aware that a smaller tank is less stable than a larger one, meaning that temperature and water parameters can change on you quite quickly. I would still suggest using a skimmer, regular water checks and changes.

As far a sessile inverts are concerned, they are okay as long as they wont sting the corals, dont mind low water temperatures (bimacs are not tropical) dont mind being covered in substrate when octo starts digging and dont mind being being moved about the aquarium if octo decides to redecorate. Oh, and dont mind low light levels. It can be done but those are the drawbacks.



TONMO Supporter
Mar 15, 2003
I've kept octos in tanks with green cup coral, and had no problems...but, it was a 55 high, the corals were perched on top of the live rock wall, and the octopus tended to stay towards the bottom. It was also a dwarf species, so it never became large enough to do things like pull the rocks apart, etc.

With a bimac, I wouldn't try it.



Dec 22, 2004
The big trap to avoid is making sure the larger tank is ready come time for the bimac. If you were to hypothetically set up a 75 gallon tank the day the baby bimac arrived and was put in the 20, then the 75 might still be weeks away from being ready when the bimac outgrows the 20.


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