Octopus bimaculoides (Bimac/Californian Two-spot Octopus) Care Sheet
"Ollie", about 9 months old -- Photo by Nancy King
Description 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, NO2- 0, NH3 - <30 ppm, Copper - 0 Octopuses are very sensitive to Copper (Cu), ammonia (NH3) and nitrite (N02), but they can tolerate small amounts of nitrates. Regular partial water changes are recommended, 10% weekly or 20% biweekly.
"Inklet", around 3 months old -- Photo by Carol Sauer
Feeding Hatchlings are fed amphipods or mysid shrimp. Some are then fed baby clams and small crabs. (The clams can be placed in a small shell or shallow bowl.) Young octos may be given ghost shrimp, which are easier for them to catch than shore shrimp but are not suitable for long-term use. When they are small, they can also eat hermit crabs. Most will accept only live food until they are several months old. Then they can be offered thawed frozen shrimp, fresh scallops, live fiddler crabs, live shore shrimp and eventually larger crabs (crabs should be smaller than the octo's mantle). Some will take pieces of fresh fish (never use goldfish) All seem to like crayfish. Never add more food than the octo can eat at one sitting as uneaten food may die or rot and pollute the tank. Bimacs three months old or less should be fed more than once a day.
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