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Sanjay Joshi
Feeding a Reef Tank
May 3, 1998

In the past years, the reef "experts" advocated minimal feeding of reef tanks to limit the amount of nutrients in the reef tank. I have been feeding my reef tanks for several years now, and believe feeding a reef tank is beneficial to the health of all life forms present in the tank.

The early advice of not feeding reef tanks was based primarily on the notion that reefs are very nutrient poor and the reef habitants, esp.corals could generate all their energy requirements through photosynthesis and fish could survive eating off the live rocks. Adding food would only increase the bio load on the tank and hence the nutrients (nitrogenous products, phosphorous, etc). Feeding regimes often touted were feeding sparingly once every three days.

I am going to focus the talk primarily on SPS coral, but it should be generally applicable to all reef tanks. Let me first start with a few facts on coral nutrition. Hermatypic Scleractinian corals (primarily SPS corals) use two modes of feeding - Autotrophic and Hetrotrophic. The autotrophic mode involves translocation of the photosynthetic products produced by the symbiotic zooxanthallae to the coral polyp tissues. The corals spend energy for the following functions: respiration, mucus production, growth and reproduction. Research has shown that the total energy demand cannot be met by photosynthesis alone. Respiration accounts for 60-70% of the energy budget of the coral, and for most hermatypic corals the ratio of gross photosynthesis to respiration is slightly greater than 1. Hence corals need to provide the additional energy needs via other means. The other means used by the corals are the hetrotrophic mode of feeding. Hermatypic corals posses the unique ability of making use of all modes of feeding known in sedentary benthic animals.These modes of feeding are:
1) Predatory prey capture by the polyps (zooplankton capture)
2) Sedimentary filter feeding using mucus nets (bacterioplankton)
3) Consume DOM (dissolved organic matter) via active transport of molecules through cell membranes

To determine what corals feed on in the wild, researchers evaluate the gut content of corals in the wild and also experiment with the animals in laboratory. Evaluation of the gut contents of a Monastrea coral contained copepods, ostracods, mysids, menatodes, polychaetes and other zooplankton. Suspended organic material ingested by corals via sedimentary filtration included bacteria, protozoans, detritus, feces of fish, etc. The size of prey captured by the polyps can be larger than the polyps. Interestingly, it seems the scleractinian corals rejected algae and other plant material. Research indicated that even if plant material was ingested it was not digested and regurgitated. This has interesting implications for the hobbyists since it leads to the conclusion that "green water" or phytoplankton (micro marine algae) may not be a suitable food for hermatypic scleractinian corals.

Some of the laboratory experiments were conducted using Artemia Nauplii as food. These are basically a form of zooplankton. The polyps easily captured nauplii of size 0.7-0.9mm. Corals with larger polyps (e.g pocillopora, stylophora) also captured Artemia nauplii upto 1.4mm. Research in predatory feeding has shown that, even in corals with polyps active in the daytime, polyps hunt more efficiently at night.

In ambient conditions on the reef (with wet bio mass of zooplankton ranging from 0.5-4 mg/L, bacteria 1.5-3 X 10^6 cells/mL, and DOM ranging from 0.5-2 mg of C/L ), as a rough average - scleretnianian corals could compose their energy balance as follows: 60-70% via photosynthesis, 10-20% predation, and 10-20% by feeding on DOM and bacterioplankton. The hermatypic soft corals are basically similar in respect to the scleractinians, but there is a wider range on the degree to which autotrophic sources of nutrition are used. Most researchers are of the opinion that octocorals are in general weak predators compared to the scleractinians, and may ingest passively floating particles of detritus, forminifera, eggs of slow moving larvae of inverts, etc.

Feeding Strategy: If you are convinced that reef tanks need to be fed, the next set of questions relate to feeding strategy. What should be the frequency of feeding?

Ideally, maybe the frequency of feeding should be targeted to maintaining a base level of plankton, similar to that found in the reefs. I have not given it much thought on how to do this I just try to feed my tank at least twice a day. Once in the morning before I go to work and once at night just before the lights go out. Another mode of feeding that is often used, is to feed more infrequently but to flood the tank with food, turn the skimmer off and let the corals feed for a few hours, before turning the skimmer on again. Personally I prefer the "less food more frequently" approach. A word of caution here. Don't starting dumping a lot of food into your tank right away. The population of bacteria and other life forms to process the increase in food takes time to build up. The population of bacteria and other zooplankton in the tank is also a function of the available food supply. So if you are starting to add more food to the tank, do it gradually.

Should we feed the higher life forms (e.g fish) and let the others take care of themselves, or should we attempt to feed all life forms in the tank? Given my current lack of knowledge on the availability of food for all the various life forms in the tank, I have been taking the approach of trying to feed all the various life forms with the hope that their nutritional needs will be met. My feeling is that if I can get the lower life forms (copepods, amphipods, mysids, nematotes, etc to live and possibly multiply) they will provide a more stable eco-system that will require less maintenance in the long run, and provide a larger food web for the corals.

What to feed? Since hermatypic corals are primarily carnivores, the best food may be live zooplankton. But I don't have access to good source of live zooplankton, nor have the ability or time to raise them. In the absence of such food, home brew blended food mix, Artificial Plankton and Rotifers, phytoplankton, rotifers and artemia nauplii can be used for food. My food recipe (based on what others have also used sucessfully): Here is my recipe for food that I have been using for a while now. My goal with this recipe was to be able to feed the corals as well as the fish in my tank. I don't really use a fixed formula but wing it as I go along. I basically go to the sea food section in the grocery store, and pick up several shrimp, squid, sea scallops, mussel, clams, etc. that I can find. The other main ingredient I use is Nori. Nori is a great food for the fish, and the herbivorous fish love it. In fact, all my fish including the lone anthias will eat nori. Nori can be found in any oriental store (just make sure and get the unflavored kind). I also add other dried sea weeds that I have been able to find in the Chinese and Japanese grocery stores.

I first throw the nori (and other seaweed) into the blender and shred into small pieces. Do this while its dry and it breaks up into nice size pieces. I remove most of it and leave a hand full in there and then add half the sea food mix along with some water and blend it into a fine liquid paste. Then I add back the rest of the nori, the remaining sea food mix, along with some spirulina flakes, vitamin drops, some yeast and chop it in the blender so as to give some larger chunkier pieces. Place the mix into the freezer bags and spread it thin in the bag to allow breaking off pieces easily, and freeze I figure the finely blended stuff will work fine to feed the filter feeders and corals, and the larger pieces along with the nori works well for the fish, and the several serpent stars that I have.

The exact proportion of each is not really all that important, I just try to make sure that there is enough variety to satisfy all the live critters in the tank. I have been using this for over a year now, and has worked great. I have recently experimented with adding broccoli, carrots and spinach to the mix. I have seen the tangs eat the pieces of spinach, broccoli, and carrots. Some other ingredients that I have added to the food include fresh fish, brine shrimp, freeze dried plankton, dried blood worms, and other fish food I have laying around. The basic idea was to create a one shot food recipe that will take care of the complete spectrum of life forms in the tanks. I feed about a 2" square piece of this "gourmet" food every day in my 180G tank.

Recently, I have been adding a "pinch" or two of Artificial Plankton and Rotifiers (APR) that is made by OSI and available through Aquatic Eco Systems. Aquatic Eco systems also has a wide range of larval feeds intended for clam, osyter, and other aquaculture that may be very well suited for feeding reefs. If you try anything other than APR, I would like to hear about your experiences with it. After using the APR, I started to notice increase in the number of sponges and filter feeders in my tank Also, the existing sponges increased in size. About a month ago, I also got some of the cryo preserved microalgae that Craig Bingman mentioned in his article in Aquarium Frontiers. .I have been using 10-12 drops of the concentrated algae in my reef, every 3-4 days. I turn the skimmer off, for several hrs when feeding micro algae, to keep the food from being removed by the skimmer. .I bough the marine algae with the intent of feeding the SPS corals, but it research seems to indicate that hermatypic scleracatinian corals do not feed on algae matter. .But I will still continue feeding it, as means of possible supplying food to the filter feeders and the other micro fauna in the tank that may ingest it and possibly benefit from it.

Conclusion: I personally believe in feeding my reef and trying to provide a range of food that will support a healthy, wide range of life forms in the tank. Right now the approach I am taking can best be described as "feed more, skim more" approach, rather than creating a "true ecosytem" approach and trying to provide a self sustaining food web. I'll leave that to Eric Hugo and Ron Shimek :-) This talk has probably raised several questions, which should create some interesting discussions. Unfortunately, I wont claim to be an expert in coral nutrition, so don't be surprised if I answer some questions with "I don't know J". should have been "i dont't know" :-) OK. Open for discusssion and questions.

Is microalgae growth a problem when feeding a reef?

I have seem some increased growth of micro algae on tank glass, which is not really bad since it releases back as food when i clean the glass .

I recently purchased a tubastrea and am having trouble with it. I tried tubifex worms but they don't seem to work.

The food mix I describe can be used very sucessfully with tubastrea. Just add a little teaser near it to first get it to open up.

I've heard people say that gonipora may need a "nutrient rich" environment to survive over 1 year. How do you make the tank "nutrient rich"?

Look at the numbers I presented for the average ambient conditions on a reef. May be if we try to maintain those levels it may help in keeping Gonipora. I have not kept one since my first attempt 5 years ago. May be I should try it again now

What does DOM stand for?

Dissolved organic matter.

If corals can indeed ingest DOM via active transport at the levels found in nature, What is the effect on the same coral in a reeftank, with considerably higher DOM?

Good question, one that I cant really answer with confidence. My guess is that given the adapatability of these corals, they may be able to adjust thier basic intake of various forms of "food" upto a certain extent

You suggestiond on feeding are for a reef running a skimmer, correct? Any suggestions/cautions on feeding a skimmerless reef?

Sorry, I have not run a skimmerless reef, so I will stay away from making any wild ass guesses :-)

Is there any problem with using oysters as part of the food mix?

I would think not. I even used octopus once and had some dye in the food from the octopus. I have just been informed by Eric Hugo, that oysters may be a good food item since they have an anti-vibrio capacity.

Do you have a point of contact for Aquatic Eco Systems and cryo preserved microalgae that Craig Bingman mentioned in his article in Aquarium Frontiers

Aquatic eco sytems has a web site, that I think is (will need to double check). for the cryo preserved plankton see CB's article on aquarium froniters.

Do you target feed sps corals (such as stylophora) or generally feed the entire tank at once?

I used to target feed, but now I just feed the entire tank. I have strong enough flow in the tank, it gets spread around very quickly.

Please discribe breifly the bioload in your tank?

My tank is a very packed SPS coral tank (180G), with about 20+ starfish, 2-3" sand bed and 15 fish. several shrimp, and sea cucumbers.

Is it ok to buy dated seafood, or should the fish get the fresh stuff?

I dont see any problem with the dated stuff, I have bought some shrimp before that the groceery store was going to throw away, as not fit for human consumption.

Where do you get the APR product?

Aquatic eco systems.

Do u have lysamatas, and if so, how do u keep them from trying to pinch the food from the corals?

THe food is basically floating all over the tank, so pinching is not really a problem. Piching only becomes a problem if you feed in chunks that dont fall apart

Have you tried Wasatch's Velvet Green and Rotifers. You said that you don't have a good source for rotifers. Do you think that it is cost prohibitive to buy them from such a source?

I have not tried Wasatch's Rotifiers... if I do (an I think I will to get a culture going using Moe's V8 juice method) it will only be to get a culture. Too expensive to pay for shipping every time.

Does scraping algae off the glass release toxin into the water?

I would doubt it would relase toxin into the water. In fact the diatoms and micro algae scrapped of the glass would make good food.

How do you feed that 2" square of food? (eg Do you thaw it in tankwater?)

I just hold in front of a strong stream of water from one of my pumps. I have even fed frozen chunk to an anemone without trying to explicitly thaw it

I would be interested to hear more about the fact that SPS do not utilise phytoplankton. You said that the researchers still found it in their gut though, didn't you?

The few papers and references that I came across all seem to indicate that the algae products are not digested by the SPS corals. Clearly the dendroneptya do utilize it. I will be glad to share the reference with you if you contact me later .

Do you use a plenum? or just sand substrate?

I just have 2-3 sand bed. NO plenum. All live sand from the Keys (when it was legal to get)

Have you ever considered cultiavating your own rotifers and green water?

Yes, I have.. but I am not interested in creating more work for myself. I am trying to see if I can find hassle free substitutes. I am lazy in that respect :-)

© 1998

Created by liquid
Last modified 2005-02-07 05:56