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which octo?

Aug 26, 2008
i have a 75 thats been cycling for a while and im ready to add fish. im interested in octos and wondering if anyone can answer some questions for me. ive been researching them for forever but i figured id get some answers from people who actually keep them. i also have a 29 gallon reef/seahorse tank with about 5 seahorses and none have died for about a year now so i guess you can say im experienced. ive also been told that octos are easier to keep but im not to sure how true this is haha. i wanted to know first of all what type of octos can be put in a 75 tank? i relize the top has to be secured, but to what extent? can they lift up the glass with a weight on it? i would also like to know how active they are? would you be able to see them swimming around during the day? or are the mostly nocturnal. also how dangerous are they (not including the blue ring). is my hand in any danger when im cleaning the tank haha?


Staff member
Sep 4, 2006
To get an idea about keeping octos, read through some of the journals and watch the videos posted there as you don't get much closer to people who actually keep them than the first hand experiences posted.

With a 75 gallon you can keep any of the commonly home housed mid sized octos (bimac, aculeatus, briareus, hummelincki). There is debate about cyanea and vulgaris needing larger tanks and the dwarf would never be seen. The mid-sized are easily adapatble to early evening hours (hummelincki being fully diurnal naturally - bimac may be as well).

There are a number of discussions on retro fitting a lid and how to secure it on the Tank Talk forums. My preference is to line the tank with a recessed acrylic rim (you can use silicone should you ever want to remove it) to create a lip and then use acrylic to make a hinged cover that fits snuggly. Alternate successes with better ventilation is the use of pre-made or custom cut screen but you will find many suggestions and photos for ideas in the forum.

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