Octopus bimaculoides Care Sheet (two-spot octopus)

By Nancy King


"Ollie", about 9 months old -- Photo by Nancy King


O. bimaculoidesis a medium sized octopus, reaching a mantle size of 7 inches (17.5cm) and arms to 23 inches (58cm). Some remain smaller than this. The bimac is not usually heavily textured and has several common colors, such as grey with yellow splotches. O. bimaculoides can be recognized by the false eyespots on its mantle below its eyes. Other species have these ocelli but there is an unbroken blue chain as part of these dark eyespots on a bimac.

Conditions for Keeping a Bimac

A bimac should be kept by itself in a 50-gallon or larger species tank. The tank needs to be well cycled and mature, which can take up to three months to prepare. The tank should be covered and well sealed to prevent escape. Bimacs like a sandy substrate and caves of rock or several lengths of PVC pipe to hide in. Bimacs tolerate a wide temperature range, ideally around 65-72 degrees F. (18 – 22 degrees C) in the home aquarium. They don't need a lot of light – a 30-watt daylight spectrum lamp for 8-10 hours/day should be enough. All overflow holes and powerhead intakes should be covered with mesh or netting. A sump could be used to house all filtration and other equipment to keep them safe from the octopus as they can interfere with fittings.

The water must be RO or RO/DI water and the tank must be provided with an over-spec filter system. Most people use a wet/dry filter, powerhead, and also a good quality protein skimmer (very useful for the heavy waste of an adult octopus, and also to remove ink).

Water parameters

Salinity - 1.026, pH- 8 – 8.4, NO3 – 0...
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About the Author
Nancy has an interest in all things cephy but especially octopus behavior. She maintains two saltwater aquariums and has kept O. bimaculoides and O. briareus as well as many other invertebrates. She joined the TONMO.com staff in March 2002 with a background in management, editing and technical writing in technology companies. She enjoys helping people with ceph keeping, including writing articles. Nancy also has a strong background in art and currently works in precious metals and watercolor with a goal of producing high quality art with marine themes. She holds an M.A. from the University of Wisconsin and presently lives in Dallas, Texas - only five hours from the Gulf!


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