What do corals eat??

This is a question that we should ask more often. Most corals are animals that live in symbiosis with tiny dinoflagellates called zooxanthellae. These dinoflagellate are chloroplast endowed that live under the coral tissue and produce sugars from photosynthesis, which are released for the benefit of their host. This makes the majority of corals to obtain their main nutritional sustenance just by placing them under a light source of appropriate intensity and spectrum.

But…is this enough? We note that the corals grow and live for many years in our aquariums eventhough we don't feed them any other way and tend to conform. Figure out that we suddenly start to feed ourselves with water and sugar, can we live like this? The answer is obvious: no, Although we will surely resist long. Well that's what happens to many corals when they reach an aquarium. Alright, maybe not so much, and I may be exaggerating because we can not compare the needs of a coral and a human, but you understand me, don't you?

Corals on the reef receive a nutrient flow, mainly zooplankton almost continuously; ocean currents carry this protein rich food from the colder waters to tropical reefs. This is something impossible to recreate in our aquariums, We can not toss zooplankton continuously without seriously impairing the water quality. But there are methods and practices that significantly benefit our aquarium corals, let's see what feeding mechanisms has a coral.

There is a third feeding mechanism: nutrient absorption.

A coral is able to absorb dissolved nutrients in the water through its tissue. And I do not mean only nitrogen compounds which greatly concern us (and so necessary although some hobbyists strive to rid them off the water), but also fatty acids, amino acids, vitamins…

Acropora Pearlberry

Corals in the aquarium.

In some respects we can not imitate nature, it is not possible to maintain the macro nutrients flow continuously without affecting the water quality, but we can provide this food, as well as amino acids and fatty acids in controlled manner.

Macronutrients, feeding polyps.

Each coral has its neccesities and skills when it comes to ingest food through their polyps. Let's see the main groups and how can they be fed:

– Long polyp stony corals (LPS). They have large oral openings flanked by large tentacles prepared to catch and eat from small food particles to small fish in some cases. Examples of these corals are trachyphyllias, catalaphyllias, blastomussa, caulastreas, etc.

– Short polyp stony corals (SPS). Their mouths are tiny and are equipped with small tentacles of up to 10 mm long in some acroporas but they are usually shorter. Although they can catch relatively large particles, they can only ingest those of a lower size up to 60 um. Many species show a feeding response by secreting a sticky goo at which food particles attach to be then recovered and placed on the oral disk. Examples of these corals are montiporas, seriatopora, styloporas, poccillopora, acropora, etc.

– Soft corals. Under this denomination there are many families of corals, many of which have evolved to the point of being unable to catch food particles, as for example pachyclavularias, briaerum, xenias, etc.

Acropora granulosa

The benefits of feeding corals.

Hard corals' calcification rate on a healthy reef can reach 12 kgs of Ca(CO)3 per m2 and year (Kinsey, 1985). In the aquarium as a closed system will range between 0,5 and 6,5 kgs of Ca(CO3) per m2 and year (Carlson, 1999), but if the aquarium water is saturated above 9 ° dkH and is intensely fed they could reach 20 kgs of Ca (CO3) (Bingman, 1997)

My recipe.

One of the pillars of coral feeding in the aquarium are the fish feces. Have enough fish that are well fed (pellets, flakes, frozen food, seaweed…) will provide food to the corals almost continuously. However, when you have many more corals than fish, it will be better to feed them with some specific food.

I have tried so many recipes and they all have something in common: it is essential to begin to use them sparingly and be very slowly increasing the amount to give time to the system to adapt and don't deteriorate the quality of the water. I feed them in two stages:

  • Phytoplankton by a dosing pump. I use a gel that combines tetraselmis, nannochloropsis and phaeodactylum in similar proportions. This gel is dispensed into the tank every hour, so that there is always a small amount of it in the aquarium water, similarly to as it happens in nature, with no peaks or valleys. Few corals are interested in phytoplankton, but after a few days the number of copepods, rotifers, ciliates and other small invertebrates is so high that some of them end up in the mouth of corals in a natural and continuous way.
  • I mix different zooplankton kinds and crustaceans and molluscs flour with a particle size of between 5 and 100 um. I enrich it with an amino acids complex, vitamins and fatty acids. I pour it at night, after the lights are turned off, in three incremental portions: the first one is small and its function is not other than to tell the corals: get ready for dinner, to which they respond extending their polyps, A few minutes later I pour half the mixture and after one hour the rest.

There are many other recipes, among which I would highlight the so-called pappone. It's a blend of oysters, mussels, clams, prawns and sugar. All finely crushed and frozen in small cubes. I have never witnessed such feeding response in acroporas, they extend their polyps and secrete an incredibly abundant slime. The downside is that it is a food that quickly contaminate the water if you do not have a powerful filtration system and is to be used with great restraint.

Will you tell us your recipe?