Reefkeeping 101 -
Let's Fatten Them Up!

Feeding the First Fish

Rock is cured, water looks good and we are ready for some livestock. Adding fish to a tank is not usually a problem. The wise aquarist always makes the owner of the {local} fish store feed the fish they want to purchase before they hand over their hard-earned cash. Buying fish on-line is more of a crap shoot in that one doesn’t know about the new fish until the shipping container is opened. One of the prime purposes of having a quarantine ( QT ) tank… What? You don’t have a quarantine tank? Then read An Ounce of Prevention before even thinking about adding any livestock. New fish have had a hard journey to your door and need a quiet place to relax before they join the general tank population. It allows observing them for signs of disease but also allows the fish to adjust to its new environment including what it will eat.

If you are lucky the fish has been eating dry flake food during the transport period, and that is great. Most major brands of marine fish food provide the nutrition the fish needs, and having fish that will eat it is a real benefit. Just remember that we may have some dietary specialities to consider; tangs need a diet high in vegetable matter, while angels like a diet with some sponge matter, their favorite food, included in the blend. Fortunately the food manufacturers have come to the rescue and have foods that appeal to most types of fish, as well as mimicking their natural diet.

Alas, this is not a perfect world and marine fish can be picky eaters. Some want frozen food or fresh food. Others, like Mandarinfish (Dragonets), refuse most food unless it is live. I once had a snowflake eel that insisted on being hand-fed a shrimp every evening when I got off work (Note: not a good habit to encourage if you have a moray with sharp teeth). During the QT period you have a good chance to find these picky eaters and select foods that are more pleasing to their epicurean palates. Quarantine is not only a means to observe for disease but an important stage in helping fatten up a fish that is often malnourished during transport and needs time to recuperate.

Many reef keepers make homemade preparations of fresh and frozen seafood for their charges. There is no true recipe for these preparations but most include shrimp, crab and clams along with whatever the reef keeper feels is appropriate. The food is generally placed in a food processor and chopped to the desired consistency; coarse for large fish and fine for smaller species. Many use the same blend, chopped very finely, to feed corals, anemones and other invertebrates.

Invertebrate Chow

I’ve always been somewhat skeptical about these homemade, or for that matter many store bought, foods for general feeding of corals and anemones. These animals use stinging cells called a cnidocyst (pronounced "ni do sist") or nematocyst to capture prey. Many people falsely assume that merely touch triggers these stinging cells to fire. If touch alone triggered the action the coral or anemone it would be wasting huge amounts of energy for nothing. The reef is full of non-food particles that would make the cells attempt to capture these inert particles. When a cnidocyst fires, it will not recharge but must be replaced with a new cell. That takes energy, so during a storm that stirs up the sea bed, a coral would fire all its nematocysts at sand particles without catching much food. It would now need to replace those cells before it could catch new prey. The little food it did capture might be less than what is needed to replenish the lost stinging cells. There would be a net energy loss and the coral would not survive for long.

Mother Nature, truly wondrous, adapts to such predicaments. Successful corals and anemones probably have multiple response mechanisms. Chemoreceptors most likely look for chemical signatures that prove that it is living tissue not just a fine sand grain particle. Size is probably also checked by communication between the cnidocyst cells. If too many are touched, it is probably a giant grouper and, too few, a bacteria, not worthy of expending energy. Only when it “smells” right and “feels” the correct size do the nematocysts fire and impale their quarry. Natural selection has probably refined these talents, over time, to choose the most desirable prey.

My own belief is that we need some natural foods for good coral culture. That means having a supply of living plankton. Growing our own is not all that involved and requires little expense. Have some clear plastic pop bottles, a shop light, aquarium air pump, plastic tubing and an airline valve manifold? Then you have the equipment for setting up a food production booth.

Growing the Veggies

The first step is to grow a garden of the ocean’s staple, phytoplankton. This is a micro algae and is the base of the food chain for the reef. When talking algae we are talking about HUFA - Highly Unsaturated Fatty Acids - and the king of producing that is an algae named Nannochloropsis oculata. Yes folks, when it comes to having “good” cholesterol these are the champions of marine algae. About a third of their body weight is Eicosapentaenoic acid (EPA), an essential ingredient for invertebrates. They are also widely available for culture purposes and raising some is pretty easy.

To start a culture, cleanliness is wise, so we need a fairly sterile environment to get things started. You can use any clear container but empty 2 liter pop bottles are very popular. Wash them well and rinse thoroughly. Fill with tap water and add a few drops of bleach and let sit over night. Empty and let dry the next day before you set up the culture station. Do the same with air line tubing that fits your air pump. Using some rigid plastic tubing to extend into the bottle is better than playing with the flexible type as it stays in place. You can drill a hole in the pop bottle cap if you wish to hold the tubing but clean cotton balls can also be used. Don’t use any air stones as the fine bubbles make the system into a protein skimmer and would float the algae to the top of the bottle. Extend the rigid tubes into the pop bottles, fill with new seawater mix and hook up your air pump. Set the air flow rate to produce about 2-3 bubbles per second. Don’t use water from the display to start a culture as the bacteria in it will take over the media in short order.

Purchase a shop light fixture and equip it with two daylight fluorescent tubes. One can be a grow light if you wish but the daylights are cheaper and will do the job. With the first bottle set up, you should now make up three more bottles and connect them all using a manifold to the air pump. Since the culture takes about a week to mature they will be needed to provide a continuous supply of phyto.

Ordering Supplies

It is now time to order supplies. Algae eat just like everything else in this hobby, well maybe the reef keeper who has spent his Big Mac money to purchase a metal halide hood doesn’t eat, but even though algae feed mainly on carbon dioxide and light they do need a little supplementation. Your phyto culture will also need fertilizer to supply things like nitrogen and phosphorus, essential to keep them growing strong. If you surf the web you see people using Miracle Grow or even Scott’s Turf Builder Plus Halts to feed their micro algae. Don’t do it! Yes they provide the essential elements but often too much and can contain ingredients you don’t want to enter your tank. A guy named Guillard came up with an algae fertilizer formula close to fifty years ago that contains what micro algae need to flourish. Called Guillard’s F/2, the F/2 stands for half strength; it contains all the nutrients the culture will need without adding huge amounts of heavy metals or other contaminants into your tank. It is the first order on your shopping list. Next we need the algae themselves. They can be bought as solutions or, better yet, algae wafers. The wafers are a culture on a disk and can be stored, if kept refrigerated, for several weeks. You will certainly want some Nannochloropsis oculata but also a second strain. While N. oculata is high in one form of HUFA they lack a second, called docosahexaenoic acid or DHA. For this you need some Isochrysis galbana and not just any Isochrysis. The type you want is T-iso, and it vacations off the coast of Tahiti. It is high in the second type of essential HUFA. The two phytoplankton’s will be mixed when feeding the tank, thus supplying both essential fatty acids and their corresponding vitamins.

T-iso is somewhat finicky in its culture requirements but is not all that hard to grow. I’ve had good result with cultures at room temperature and a slightly reduced salinity, by removing two or three cups of salt mix water first, and adding the same amount of RO/DI water to a 2-liter bottle. The reduced salinity should do them well. Both N. oculata and I. galbana will grow at normal room temperatures and common reef salinity but slightly lower salinity and higher temperatures do help. Set up a T-iso line of four bottles just the same as was done for N. oculata.

Setting It Up

Once the cultures and food are received you are ready to make “green water.” Fill the soda bottles with salt water mix, using the diluted saltwater version for T-iso. In a manifold setup it is best to make sure the water levels in each bottle are equal so air reaches each culture container. If one is lower than the other it will receive the lion's share of the air supplied. Turn on the air and lights and add a teaspoonful of Guillard’s solution. Give it an hour or two to aerate and add the algae culture wafer. If using a liquid culture then follow the dose recommendations of the supplier. Lighting should be on from 14 to 16 hours each day and using a light timer switch is good practice. Some people illuminate for 24 hours but from papers I’ve read, that may reduce the nutritional value of the culture as it inhibits sugar to fatty acid/protein production. Your culture at this point should have a pale green tint (brown for T-Iso). Adjust the air volume so there is no settling out of the alga, but don’t have it so violent that it raises it all to the surface.

Sit back and wait two days then set up a second bottle. Add a cupful of culture from Bottle Number One to this new bottle, and do the same with a new bottle every other day until you have four bottles running concurrently and sequentially. Remember to replace the cup of culture removed with new saltwater mix. By that time the first culture should be dark green, brown ( T-iso ) and full of nutritive algae. It is now time to harvest the first culture. Some use the culture to feed directly to the tank but, be warned; the algae that are not immediately consumed will start reproducing in the display tank. If the growth rate is faster than the consumption rate a green display tank results. If you use this method you want a canister filter with polishing cartridge. About 8-12 hours after feeding run it to clear off the uneaten algae.

This culture method can supply algae for quite some time but after awhile bacteria enter the system and will eventually take over. For commercial algae culture enterprises, great pains are taken to ensure aseptic conditions where everything that touches the culture is kept sterile. In our small scale system this tends to be overkill as a new culture can be started at any time. Just be sure to bleach-disinfect the equipment and containers before starting a new culture.

Nature’s grass catchers

Fortunately there is a way to provide the nutrition of the algae without turning the display into an algae culture vessel. That is zooplankton; animals that feed on algae and condense its nutrition into compact bits of food suitable for coral and other invertebrate feeding. Probably the most well know critters are “sea monkeys,” brine shrimp, and they are simple to breed. Their basic problem is they lose their nutritional value less than a day after hatching when their yoke sac is exhausted. Feeding them algae culture is a great way to fatten them up and restore their food value. I won’t go into breeding them as there are a ton of papers that detail the process. I’ll provide links for those of you that wish to go that route at the end of this article.

Another great food source is rotifers. These tiny critters are like individual grass catchers and can sweep the water column clear of algae in very short order, far faster than brine shrimp. Most rotifers are freshwater but a few of them are from salt or brackish water. A species known as Brachionus plicatilis is the most commonly bred saltwater variety. They are a fairly large, slow swimming organism and breeds prolifically under fairly easy to duplicate conditions. Since we are breeding these in fairly small quantities to feed our corals we don’t need fancy breeding containers. A couple of those 5 gallon jugs they use to supply drinking water coolers are just fine. You also need two small air pumps and some air line tubing, both flexible and rigid. Since in this case the two cultures we will be starting will have differing water levels it is better to use two pumps rather than a single one as the water levels in the containers will differ. It is easier to use liquid live cultures, ordered by mail, rather than cysts. You start your culture by placing three liters of saltwater mix and one liter of RO/DI in your first container and start the air. Adding a drop or two of Kordon Amquel or other saltwater ammonia remover is often a good idea as rotifers are easily killed by high ammonia levels. We will be using live algae to feed them which lessens the chances of ammonia toxicity as the algae uptake ammonia but the ammonia remover is good insurance. Next add two cups of algae from your culture. You can use it as liquid but I like to filter it through a coffee filter and re-suspend it in two cups of fresh SW mix. This limits the fertilizer in the algae culture from entering the rotifer tank. Add your rotifer stock culture next. The water should have a light green tint. If it loses its color in less than 12 hours add two more cups of algae to the brew. The following day add two liters of saltwater, a liter of RO/DI, and two more cups of algae culture. Repeat on the following day. By this time you may find that your culture takes the green from the water in less than 6 hours and it is time to feed on a more frequent basis. Feeding a cup every six hours is preferable to feeding twice a day.

By Day Five you probably will need to feed a cup of algae culture every three hours and if you have a dosing pump you might consider continuous feeding. The aim is to keep the culture a light green (brownish green if you feed both N. oculata and T-iso at the same time). If you feed both types of algae use equal amounts as the N. oculata contains more EPA than T-iso contains DHA. Sadly, rotifers don’t store food and need to eat continuously. If they run short on food they tend to go sexual and that is not good for the culture.

Harvest Time

At Day Five you can also make your first harvest of rotifers. The first step is to gut-load the rotifers with algae. Give a heavy feeding of both N. oculata and T-iso, about a cup of each, to the rotifer culture two to three hours before the harvest. Next harvest the rotifers themselves. The best way to do this is to remove about half a liter of rotifer culture and filter it through a fine rotifer sieve; the coffee filter trick works in a pinch. This step is especially important if you have been adding liquid algae culture directly from the culture vessel. By filtering off the water you avoid getting algae fertilizer in the display tank. Once captured, just wash them off the net, screen or filter into the display tank. Replace the amount of culture water removed with fresh full strength seawater. At this point in time a reduced salinity is not required as the culture will be reproducing fairly fast even at normal tank salinity. On each day you can remove a half liter of rotifers and use them to feed the tank. On Day Seven, start up the second culture vessel. Set it up in the same fashion as you did with the original culture and add a half liter of culture from the first vessel and use it to seed the second.

A single culture should be self-sustaining for quite some time but I like to use a 12-day cycle. Here you harvest culture one for 12 days then dump it. Clean the vessel and set it up anew, seeding it with rotifers from culture number two. I think you will find this method reduces the chance of a crash. This continuing renewal of both algae and rotifer cultures reduces the chance of a bacterial outbreak, over crowding, and toxin buildup in the culture.

Bigger Game

Feel like having even larger live food for your tank? It just so happens that copepods and mysis shrimp love rotifers. You can set up a remote refugium to raise either one using gut-loaded rotifers to feed them. If you have an in-line refugium in the sump you can spot feed rotifers to it to keep the pods happy.

Rotifers are great to feed dwarf seahorses and a must if you wish to raise baby fish. Once you get the hang of the routine, it is easy to do and the major cost is mainly in salt mix. For those of you that have access to natural seawater, it is better to use dry mix as the natural seawater may promote bacteria outbreaks. That is not a major problem in a small scale culture system; if you have a crash, you can start all over at minor expense.

In closing, I'm linking you to several in-depth articles about culturing live foods. This column gave you a general approach, and the following will provide you with additional methods.

Optional Reading

Algae culture by Frank Marini
Culturing Green Water by Marc Levenson
The Provasoli-Guillard Marine Phytoplanton Center
Culturing Nanochloropsis by Adam Moore

Rotifer Culture by Frank Marini
Brachionus culture - NOAA Article

Brine Shrimp (Artemia)
Brine Shrimp Culturing by Marc Levenson
Decapsulating Artemia Cysts by Brett Kemker

Copepod Culture by Joe Thompson

Mysis shrimp
Culturing Mysid by F. Marini and M. Moe

If you have any questions or comments about this article, please visit this thread in the New To The Hobby forum on Reef Central.

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Reefkeeping 101 - Let's Fatten Them Up! - by Tom Murphy (aka WaterKeeper) -