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Many people think of members of the grouper family as a tasty main course, rather than a brilliant adornment to the coral reef community. However, reef crests throughout the Pacific to the Indian Oceans and even the Red Sea, are graced with a myriad of small brilliantly colored little fishes of this family (Serranidae), known to reef hobbyist as Fairy Basslets or Anthias.
Anthias are smallish fish by general standards, most reaching only 4 to 6 inches in length at maturity. They all display brilliant colors: red, pink, orange, yellow and some even lovely purples. Their size makes them ideally suited for reefs, especially since they feed mostly on plankton and do not display any aggressive behavior towards any other reef inhabitant.
These colors are part of their territorial display features, and actually may aid in camouflage as the light fades and with it, the colors of the reef. They have lunate (half-moon shaped) tails and fusiform (bullet shaped) bodies which allow bursts of sudden speed when need for feeding or defense. Most of the time they are slow swimmers and may not even move much for great lengths of time, except when aggressed or when a sudden supply of food becomes availabe and they need to swim to reach it.
All have, in varying distinctiveness, a bar that runs from the eye to the pectoral fin (tail fin). These fins are broad and soft, perfect for maneuvering through their coral homes. Overall the fishes shape is very characteristic and makes Anthias easy to differentiate from other fishes. Their mouths are large and in one genus Mirolabrichthys, the snout is very pronounced.
Anthias live in large colonies around branching and table corals (Family Acroporidae) among which they find shelter and a place to rest at night. They are generally diurnally active (meaning they are active during the daylight hours), and spend a great deal of time hovering above their chosen coral head, scooping up their plankton diet. The forereef and reef crest are rich in drifting plankton, and the currents bring the food right to the waiting fishes. On any given reef, Anthias colonies may be made up of thousands of specimens.
Colonies are made up of smaller groups which are structured like a harem wtih an approximate ratio of one male to anywhere from five to twenty females.
They are sequential, protogynous hermaphrodites, meaning they can change from sex to another - from male to female. They hatch as females, which are gently colored in pink and orange colors.
After about a year, some of the females will change to males. Out of that group of bachelor males some will become "supermales". It is not possible to predict how many female will change to males. The fact remains though that some do.
These changes take only a matter of weeks as color and behavioral patterns change. The ovaries degenerate and give way to the appearance of testes. Male coloration is generally much brilliant than that of the females. Male colors go from vivid reds to oranges to purples, or any patchwork combination of the above which is exactly what makes these fishes so colorful. The dorsal fin develops into an elongate filament, and the eye-to-pectoral fin bar intensifies in color.
Supermales defend their territories and their harem from neighboring supermales, while bachelor males hover around below the supermales and females. The juveniles remain towards the center of the colony. This behavior is typical of harems that are not yet ready to move to the spawning phase as, when that happens, behavior changes completely as we shall see.
If for some reason the supermale is removed from the group, e.g. through disease or predation by other fish, one of the bachelors will assume the role of supermale. Aggressive behavior can occur when this takes place to determine which one of the bachelors gains that position. There are many candidates. On the reef this can be quite a sight.
Spawing occurs just before sunset. Supermales band together and initiate zigzagging u-shaped swim patterns, ascendin higher and higher into the water column. The rest of the colony is stimulated by this behavior and follows the supermales. While this goes on, supermales become even brighter in color and may exhibit aggressive behavior towards bachelors.
At the top of the ascent, supermales pair up with ripe females and the pair display to each other by gaping their mouths and swimming in wriggling patterns. Eggs and sperm are released into the water column; whether bachelor male add their genes to the pool of sperm is not known.
Just before the daylight completely fades and darkness starts to set in, the whole colony of Anthias retreats to the coral of their choice. It is interesting to note that this may be the same one they were hovering over before but it may also be a different one.
Anthias share their habitat with other fishes such as damsels of the Family Pomacentridae, including the genera Dascyllus and Chromis. This is interesting from an aquarium standpoint as the latter fish are usually considered aggressive but, in most casese, will not bother Anthias fishes.
Aquarium care is fairly easy since they are non-aggressive and are plankton feeders. Good water quality is obviously a must but hobbist tend to ensure that this is so anyway. Because of their feeding habits, no mechanical filtration should be used on the tank and the fishes benefit from the addition of zooplankton on a fairly regular basis. If a hobbyist is unable to keep Anthias, he or she should definitely consider whether or not the fishes are able to obtain enough plankton.
They are non-aggressive to corals. They appear to really favor the presence of cleaner shrimp in the tank. They are not known to be prone to parasitic attacks except when you first receive them and when they are still under heavy stress from transportation. Slow acclimating to the tank is therefore suggested. Treating them with Vitamin C in a holding tank before adding them to the main aquarium is an excellent practice as well. Anything that can be done to refortify the fishes is beneficial and will greatly enhance the rate of success you will experience.
These fish are best kept in a small harem of one supermale and five females. They should be placed in an aquairum no smaller than 100 gallons. Lonely specimens will generally not do well.
Since Acropora is their favorite coral they will do real well in tanks where this coral is present but this is not a requirement. More important is the size of the tank and the feeding of plankton.
Should you place all females in a tank you may very well observe the sex change mentioned earlier. This may take several months before it actually happens though. The fishes first need to get accustomed to their environment, fortify themselves and be generally free of stress. Do not keep Anthias with aggressive fishes. This will continuously stress them and may cause them to jump out of the tank.
Daily if not twice daily feeding is a must. Frozen plankton can be used. In aquariums with plenty of live rock they will derive some food from the animalcules that inhabit such rock. This is not sufficient though, supplemental feeding is a must.
Caves of some sort in the aquarium are a plus but having branched coral is better. Lighting should be moderate to high but need not be metal halide type unless of course you also keep corals in the tank that needs such lighting.
In part II we will be discussing various types of Anthias.
July 1997