There is a lot of bad aquarium advice circulating on both the internet and among (less experienced) aquarists. This is especially true when it comes to maintaining a reef tank, where some techniques and homemade additives verge on the edge of black magic. Nevertheless, more than a handful of different approaches to maintaining a reef tank all work. You wind up with a lot of people trying a lot of different things.

These people post reports of success prematurely, and you never hear about the tank crash or the severe algae outbreak that happened a month later. Unlike keeping cats, dogs, and reptiles, successful reefkeeping is still in its infancy and we are all learning, from the marine biologist to the home nano-reef keeper.

A successful reef aquarium can be defined as just two objectives: good coral coloration and good coral growth. If you get there on your own, you can be proud that you made it- despite everyone telling you to try this or that, or weeding through tons of misinformation on the web. Keeping corals healthy and thriving is hard work, but the rewards of seeing your “slice of the reef” grow and thrive is all worth it. The trick is coming up with your own recipe for success.

Equipment and additives always take center stage in aquarium care. But feeding corals is often misunderstood or neglected. At the LFS, I cringe when I overhear beginners pointing to specimens and talking about photosynthetic versus non-photosynthetic corals. The usual advice is, “If you buy that one, you’ll have to feed it”.

Well folks, all living organisms on the planet have to feed. While it is true that photosynthetic corals have evolved to withstand bouts of famine, all living creatures need to eat sooner or later.

Non-photosynthetic corals naturally grow in caves and narrow passages, where current flows constantly bringing in a constant supply of food particles. They are used to eating all the time. Interestingly, almost all non-photosynthetic corals are very hardy and quite tolerant of poor water quality, unlike their photosynthetic cousins. Think of these corals like marine fish (which by the way, are also non-photosynthetic). They have to be fed regularly, at least once a day. It all boils down to feeding the right foods on a regular basis. But whether your talking about photosynthetic or non-photosynthetic corals, food is the key to success.

I tend to think that my SPS corals are like my vegetable garden. I was careful to pick a spot that gets lots of sun, and spent some time picking out the right fertilizer to match the types of vegetables I’m growing. With both sunlight and fertilizer I will get a nice crop of tomatoes, green beans, and bell peppers all summer long. I once skipped the fertilizer and wasn’t very happy with the results. The look and size of my vegetables were unappealing.

I use the same philosophy with my corals. Without proper lighting and without proper food (fertilizer) my corals won’t have the bright coloration and rapid growth that they should. Oh, they’ll survive, but they just won’t thrive.

There is nothing more frustrating than spending $50 to $100 for an SPS coral with beautiful colors, only to have the colors fade or turn brown after a month in your aquarium. Sometimes just the tip color is gone, the polyps barely open, or small bleach spots appear at the base. While additives such as calcium, magnesium, and strontium play an important role, nutrition is the number one factor affecting coloration and color loss.

Biologists have always viewed corals as unique in the animal kingdom. They are the only organism that has dedicated over 70% of its body to feeding appendages.

They are literally covered with mouths. In 1931, C.M. Younge stated, “When an animal possesses an organ or set of organs which perform certain functions with perfect efficiency, it can be taken as axiomatic that such organs are used.” Bottom line: these guys are designed to eat.

Photosynthetic corals do not use light themselves as any form of nutrition. Instead, there is a micro algae living inside the skeleton called Zooxanthellae (pronounced zoo·ant·the·lay). This micro algae is symbiotic with the coral, just like the clownfish and the anemone. Like all algae, it lives by photosynthesis and converts light to carbohydrates (sugar). These sugars, being in close proximity to the coral tissue provide the animal with a source of carbohydrates (but no proteins). In turn, the coral’s waste provides nutrients for the algae.

70% of coral surface area are covered with “mouths”

It’s important to understand that this algae is not attached or biologically connected in any way to the coral’s tissues. It just sits near the tissue as a separate, living organism. When food sources containing protein are ingested through the polyps, the sugars act as a catalyst to create a complete source of nutrition for the coral.

So in order for the symbiosis to work, the coral has to ingest proteins so it can feed the algae. In other words, Zooxanthellae requires that the coral eat solid food in order to survive. This is the symbiosis. Since corals derive there color from the Zooxanthellae, this is why lack of food causes the colors to fade.

You and I (and your corals) may be able to survive on sugar alone, but we just won’t get everything we need in terms of nutrition to remain healthy and in top condition.

Corals do derive some food from detritus, amino acids, and other compounds in the water column. At one time it was believed that ‘turkey-basting” Live Rock and getting detritus suspended in the water would provide sufficient food for corals. It has been found that the protein level of detritus is so low that the energy required to feed far outweighs any benefits. Ironically, the best looking reef tanks with crystal clear water are the worst environment for the natural feeding of corals.

Microscopic View Of Zooxanthellae

Fortunately, SPS corals are very easy to feed. I use a combination of foods and vary the recipe a bit from time to time. Like marine fish, we don’t know what constitutes the Acropora diet, so using different combinations of food sources is your best bet.

There are powdered coral foods available such as Coral Grow, Coral Frenzy, and Reef Roids that form the base of my coral mixture. I also add some frozen foods, such as oyster eggs, prawn eggs, or frozen Cylcop-eeze. Particle sizes greater than 100 microns are too big for feeding most SPS coral polyps. Save your Mysis and Brine shrimp for your LPS’s.

If you prefer, you can buy ready-made frozen foods suitable for filter feeders. There are many products available from your LFS that will do the job. I have found that these commercially prepared products are highly concentrated, so use only small amounts until you get a feel for how much to feed. Frozen fish foods, with or without gelatin binders are unsuitable for corals because particle size varies considerably.

Basic coral feeding ingredients

I mix up my coral food a few minutes before I feed. I don’t create frozen blocks of coral food ahead of time, though many people do. I first put a few ounces of tank water in a small cup (don’t use freshwater) and add about 1/8 teaspoon of powdered coral food. I will then add a small amount of frozen food which most of time is a frozen chunk of Cylop-eeze. To enrich the mixture, you can add a few drops of Selcon or a pinch of dried Spirulina (available as a powder at most health food stores). I stir the mixture for a few seconds and then I’m ready to feed.

You want to do what’s called “target feeding” your corals. Just dumping the mixture into the tank is a waste, as only a minute amount of the food will actually be consumed by the corals. Target feeding is easy to do and can be done with an eye dropper or my preferred method, using the Kent Marine Sea Squirt. This is basically a giant eye dropper with a built-in extension that no reef aquarist should be without. Turn off all circulation pumps, return pumps, etc. to make the water still. Suck up some of the mixture into the Sea Squirt. Place the tip of the eye dropper about an inch away from the coral and squeeze the rubber bulb. The coral will be covered by a cloud of the mixture. You will see the polyps close around the food particles. Move to the next coral and do the same thing. Be careful not to touch or hit the coral with the tip of the eye dropper. Doing so may cause the polyps to retract and the coral won’t eat.

“cloud of food” during coral polyp feeding

This all sounds complicated but it’s really easy to do. You don’t have to be precise in spraying the food, as it will disperse around the coral. From the time I mix the food and feed the corals, the whole process takes me less than 5 minutes.

After feeding you will see some stringy slime rising out of some corals. This is normal and nothing to worry about.

I usually turn the circulation pumps back on right way, but keep the skimmer and return pump off in order to keep the food particles circulating around the tank. I then turn everything back on in about 30 minutes. An added benefit: any uneaten food particles will work there way to the live rock and boost your pod population.

My normal feeding regime is twice a week. I have never had a nutrient problem due to feeding. If you’re worried about this, plan your water changes so you do them the day after you feed. A 50 – 75 gallon tank packed full of SPS corals won’t need more than 2 ounces of liquid food at any given time. I would suggest that you start sparingly and feed frequently. There is no hard fast rule on how often you should feed corals. Twice a week is adequate for most setups. If you’re trying to accelerate the growth of frags, then feed once a day.

Many of the things we do to improve our reef aquariums takes weeks or even months to see results. Not feeding. The effects can be seen in less than 24 hours. Observe your polyp extension just before you feed. The next morning after the lights have been on for a few hours, look at your corals again. you will see a pronounced polyp extension as the corals seem to be saying “give us some more!”.

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