The open brain coral (Trachyphyllia geoffroyi) is a great stony coral for the beginner and advanced aquarist alike. The open brain coral consists of a large fleshy polyp that can exhibit some truly spectacular colors. The open brain coral is a very easy coral to keep, as long as you have the appropriate lighting and don’t keep it with fish that will pick at its sumptuous flesh.
Difficulty: While Trachyphyllia geoffroyi depends heavily on the zooxanthellae (symbiotic algae) that live in its tissues, it also feeds on larger zooplankton in nature and should be fed in the aquarium. The open brain coral puts out feeding tentacles that extend out of the oral disc inside the mantle at night that capture its food. It is a good idea to target-feed this coral several times a week. Feed the open brain coral small pieces of frozen seafood and whole frozen mysid shrimp (if food items presented are too large, they will ingest it, but eventually it will be regurgitated). The open brain coral will also capture some of the food added for your fish community.
Physical description: The open brain coral is free-living and has a flabello-meandroid corallite with a large fleshy polyp with one to three mouths. The color of the polyp can be reddish-brown, red, gray, bright green, yellow or a combination of these colors. (Pale individuals are those that have bleached as a result of stress and should be avoided.) Some individuals also sport fine striations. When expanded, the polyp covers the corallite. This is the only species in the genus. The open brain coral can be up to 4 inches across.
Range: The open brain coral occurs from the Red Sea and east coast of Africa, east to the tropical Western Pacific. It is usually found in more protected areas, like lagoons, coastal fringing reefs or in deep water off reef slopes.
Compatibility: Trachyphyllia geoffroyi is not a very aggressive coral. However, the open brain coral does have feeding tentacles (as described above) that may sting corals that are placed too close to it. All of the coral-feeding fish are likely to pick at your open brain coral (including butterflyfish, triggerfish and pufferfish), and because of its fleshy polyp, it is often nipped at by fish that are not normal predators of stony corals, including pygmy angelfish, surgeonfish and rabbitfish. The large polyp can be damaged by the spines of sea urchins, as well.
Aquarium conditions: The open brain coral requires moderate to high lighting to thrive (it has been suggested that the bright green individuals prefer brighter conditions than the gray or red individuals). The open brain coral will do well under power compacts, T-5 and HO fluorescent bulbs, and metal halide lamps. If the open brain coral has been in a more dimly lit aquarium for a while, do not place it close to an intense light source without first acclimating it to brighter conditions (also, don’t put your Trachyphyllia geoffroyi up on top of the rockwork near intense metal halides). Bleaching will result from such photic shock. The open brain coral will do fine in weak to moderate waterflow. If placed in an area with a strong water jet, the polyp will remain retracted, and it will eventually perish. Water parameters for the open brain coral are: calcium 400 to450 ppm, alkalinity 3.2 to 4.8 meq/L and no phosphates. It will do well at water temperate of 74 to 84 degrees Fahrenheit.
Care considerations: Always pick individuals that have polyp tissue that covers the entire skeleton. If tissue damage has occurred, the open brain coral may die as a result of bacterial infections or attacks from the “brown slime” (a species of protozoa). As indicated above, the open brain coral is usually found on soft substrates with the base of the skeleton anchored into the sand or mud. Many hobbyists rest it on the live rock structure in their aquarium. This often works fine, but it is unnatural, and the coral may topple off its “perch” if and when the polyp swells up. This can lead to mechanical damage to the polyp, or it may fall into another sessile invertebrate and sting or be stung by it. If you have the room, put these corals on the sand bed. Because the open brain coral normally lives in this habitat, it is adept at shedding any sand that is deposited on it. That said, an open brain coral may suffer if it is regularly buried by active burrowers or sand-sifters. If it is flipped over by a fish (e.g., wrasse) or if falls off the rockwork, the tissue will degrade if it is not flipped back over. The open brain coral sometimes succumbs to boring algae.
Breeding: The open brain coral will engage in asexual reproduction in the aquarium. When it buds the daughter colonies usually develop around the base of the corallite. The buds can be broken off the mother colony. The open brain coral has separate sexes (that is, it is not a hermaphrodite).