Is an additional administration of food to symbiotic corals necessary, or not? Surely, the aquarists’ opinions on this point disagree, and many completely give up feeding symbiotic corals in their aquarium. However, there should be no doubt on the fact that many species of symbiotic corals take nutritional particles from the water. The zooxanthellate corals feed for over 90% on the products of their symbiotic algae, the remaining is taken in the form of floating particles, planktons and dissolved substances. Just the sole fact that the polyps of the corals are able to capture and digest planktonic organisms, indicates the need for a supplementary feeding, otherwise they would not form these apparatuses designated for the capture of plankton.
Whether an additional administration of food in a reef aquarium is necessary or not depends a lot on the quantity of present usable substances. If we breed various fishes with a high metabolism, and we feed them abundantly, then for sure the water will also contain sufficient dissolved substances without any addition of supplementary food. If on the contrary the aquarium hosts few fishes or the water is filtered and skimmed “perfectly”, then the corals will have few available food. In this case a regular administration of supplementary food can make sense. In case of many corals, mainly the soft ones, this additional nutritional provision has an evident effect, accelerating their growth like for example in the tree-shaped soft corals of the genus Nepthea. Who should be fed? Almost every species of symbiotic coral benefits from an indirect administration of food. This is also true for those of the family Xenidae that are provided with a reduced digestive tract, since they take the substances dissolved in the water through the body surface of the polyp. The large polyp hard corals, which extroflex during the night their tentacles to capture plankton, can be fed directly with a pipette, for example with a common frozen feed like the mysis. Some large polyp hard corals even accept whole frozen shrimps or part of them. The non-symbiotic corals like Tubastrea completely depend on the administration of food. In this case it would be necessary to adopt the technique of the direct dosage, and to ensure that sufficient food is available to the polyps. What type of feed should be used? For the indirect administration of food, basically every type of feed whose particles are sufficiently tiny is suitable. It is possible to use a fine frozen feed (e.g. cyclops or plankton), a special nutritional suspension for corals or even a powdered feed for fries. It is also possible to use a flaked feed as long as it is finely minced and, of course, it is also possible to mix the various typologies of food.
How to administer the foods?
The direct administration of frozen feed or of a dry one mixed with water is best performed using a pipette. Even an injection with the addition of a little tube inserted on the extremity proves helpful. In case of an indirect dosage of the feed, which is suitable for the majority of corals, a reduced quantity of food is distributed in the water of the aquarium. However, in this case “more” does not mean “better”, because the polyps perceive a too high concentration of food as “water pollution”, even stopping their food consumption and closing. The process of food assimilation requires a long time and cannot be quicken through a greater amount of food. The more food will be dosed, the greater amount of it will end in the skimmer or polluting the water. For this reason, it is preferable to administer it in a smaller amount but more frequently.