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Marine Aquarium Questions and Answers

Get the answers to the 10 most common marine tank questions.

By John Tullock

This is a commonplace question that stems from a fundamental misunderstanding of the nature of the two parasites most frequently seen in marine fishes. First, the parasites themselves are ubiquitous and cannot be "eliminated" from the aquarium. The key to avoiding an infestation is to provide conditions that promote good health in the fish population. In the ocean, the fish's immune system largely protects it from infestations of Cryptocaryon (white spot) and Amyloodinium.

In the aquarium, maintaining good health in the fishes involves — first and foremost — practicing good aquarium management, as described in this series of articles and in many other publications. When you bring a new specimen home from the dealer, place it in a separate tank for a couple of weeks to observe its behavior. This will prevent any problem that may develop in the new fish from spreading to established specimens. In addition, isolating new specimens in a separate tank makes the job of treating them much easier if a need for treatment does arise.

Should treatment for white spot or coral fish disease become necessary, the only truly effective medication is copper. Use an ionic (not "chelated") copper medication, and use a copper test kit to determine when the correct dosage has been added to the treatment tank. A copper concentration of 0.25 parts per million (ppm) is most effective. Below 0.20 ppm, the treatment will not be effective; above 0.30 ppm, the copper is toxic to the fish. Copper medications should never be used in a tank containing invertebrates, because most invertebrates are rapidly killed by therapeutic levels of copper. This is another good reason to have a separate treatment tank.

Angelfishes are somewhat more sensitive to copper treatment. Before exposing an infected angelfish to copper, attempt to cure the problem with a medication containing formaldehyde and malachite green, used according to the manufacturer's directions.

Symptoms of Cryptocaryon and Amyloodinium include rapid shallow breathing, scratching, hiding, poor appetite, loss of color and the appearance of small white dots on the fish's body and fins. These parasite problems commonly appear in fish that have recently been transported from the point of capture and in tanks that have experienced some sudden departure from good water conditions.

How can I get rid of all this algae?
It is worthwhile to point out that many species of marine life feed on algae. Tangs, angelfishes, some blennies and many kinds of snails are in this category. These species will benefit from being able to graze on algae growth in the tank. Algae becomes a "problem" when it interferes with the aesthetic appeal of the tank or when rampant growth threatens to smother delicate organisms, such as sessile invertebrates.

There is no simple solution to the problem of controlling excess algae growth because a variety of factors are involved. Of primary importance in the closed system of a marine aquarium is the accumulation of excessive levels of nutrient ions in the tank. Nitrate, phosphate, carbon dioxide and dissolved organic matter all play a role. These substances are in relatively short supply in the natural environment of the coral reef. In the aquarium, however, they can rapidly accumulate, providing "fertilizer" for explosive growths of filamentous, encrusting and free-floating algae species.

Removal of dissolved organic matter by means of a protein skimmer is one of the simplest techniques of algae control, although this approach alone will not work if attention is not paid to the other nutrients as well. Protein skimmers also tend to lower the concentration of carbon dioxide in the water as a result of vigorous aeration that takes place in the skimmer column. Step one, then, in any plan to prevent algae from taking over your tank is to install a protein skimmer and to keep it properly maintained.

Recommended Reading

There are lots of books on the market from which to choose. While most are good, some are better than others. The books listed below are on my must-have list for anyone in the hobby.

Mills, Dick. Encyclopedia of the Marine Aquarium. Tetra Press, 208 pp.

Moe, Jr., Martin. The Marine Aquarium Handbook — Beginner to Breeder. Green Turtle Publications, 176 pp.

Moe, Jr., Martin. The Marine Aquarium Reference — Systems and Invertebrates. Green Turtle Publications, 510 pp.

If your interests include invertebrates as well as fishes, you should also consider the following titles:

Haywood, Martyn and Sue Wells. Manual of Marine Invertebrates. Tetra Press, 208 pp.

Thiel, Albert. The Marine Fish and Invert Reef Aquarium. Aardvark Press, 320 pp.

Tullock, John. The Reef Tank Owner's Manual. Aardvark Press, 272 pp.

There are also many books that cover the fishes and/or invertebrates of specific regions of the world's oceans. These can provide lots of good information on coral reefs and the natural history of the marine life associated with them.

Limiting the concentration of nitrates and phosphates is a bit more complicated. Nitrate, for example, constantly accumulates in the aquarium as the end product of biological filtration. Most of the nitrogen present in foods added to the tank winds up as nitrate. Regular partial water changes are one means of controlling nitrate. The amount and frequency of water changes will depend on the particular circumstances of each individual aquarium.

Thus, one should perform a nitrate test weekly, and change water when the nitrate ion concentration rises above 10 ppm. As a general rule, more frequent water changes are required for tanks that are populated exclusively or primarily with fish, and less frequent changes are required for tanks that are largely populated with invertebrates.

Phosphate limitation presents a somewhat more complicated problem. Phosphate is ubiquitous in nature and finds its way into the aquarium from a variety of sources. These include all foods, some salt mixes and tank additives, and even your tap water. In every case that I have had the opportunity to investigate, a tank overgrown with algae also contains a high concentration of phosphate.

Keeping your aquarium scrupulously clean, and especially the removal of accumulated detritus on a regular basis, will help to eliminate phosphates. If your salt mix contains phosphates, switch to a brand that does not. You can evaluate your current brand easily by performing a phosphate test on a freshly mixed batch of water.

You should also perform a phosphate test on a sample of your tap water. If the tap water contains phosphates, you will have to decide if your algae problem is sufficiently severe to warrant purifying the tap water before use — by means of reverse osmosis, deionization or some other means. If your water requirements are small, you can purchase distilled water at the grocery store.

Filter media are available that will remove nitrates and phosphates. Such media can be used to limit the concentration of these compounds, but remember that they are of little value for a tank that has high levels of nutrients to begin with. After you have eliminated nitrate and phosphate with the methods outlined above, you can use ion-removers to help keep these problem ions under control.

One type of algae growth may be particularly troublesome in newly established tanks. Golden brown films that spread across the glass, substrate and decorations are growths of diatoms. Diatoms require, in addition to the other nutrients mentioned above, a compound called silica that is most often found in tap water. Fortunately, diatom growth is often replaced by other types of algae as the tank matures. If your tank develops an unremitting problem with this type of algae, the only satisfactory solution is to use purified water, not tap water, for making synthetic seawater.

Lighting also plays a role in algae growth. For example, in tanks that formerly grew little algae, the appearance of a bloom of diatoms, red slime algae or blue-green slime algae is often indicative of the need to change light bulbs. As fluorescent lamps age, their intensity diminishes and their spectral output changes, which may trigger a growth of undesirable algae where none was previously present. The relationship between light and marine life is complicated and poorly understood, however, making it difficult sometimes to determine if there is actually a lighting problem.

What are those little bugs crawling on the glass?
After an aquarium has been established for a while, tiny crustaceans and worms sometimes appear. These are probably introduced into the tank along with fish and invertebrate specimens, and feed on detritus and algae. The commonly observed species are capable of reproduction in the tank, and sometimes multiply to high population densities. Several organisms are in this category.

Amphipods are shrimp-like crustaceans about a quarter of an inch (6 millimeters) in length. Copepods, another crustacean, are much smaller and may appear as white specks moving around on the glass and rocks. Flatworms are about an eighth of an inch (3 millimeters) long, with a rounded head and forked tail in the most commonly seen species. They are translucent and are usually seen gliding on the glass. Nematodes are short, white, thread-like worms — usually less than a quarter-inch in length.

All of these are harmless scavengers, but their presence in great abundance indicates that excessive detritus is accumulating in the tank or that uneaten food or a dead animal is decomposing in the tank unnoticed. Cleaning the tank will lower the numbers of these organisms.

While not in the "little bug" category, bristleworms can also reproduce in the aquarium, and these may indeed pose a problem. Bristleworms are pinkish orange in color, with rows of white bristles running along the sides of their bodies. They may grow up to 3 inches (8 centimeters) in length and can infest the substrate over an undergravel filter in enormous numbers. The bristles can irritate your skin if they come into contact, and the worms have been known to feed on sessile invertebrates, causing extensive damage.

They may be eliminated, if you are patient, by baiting with a piece of shrimp or fish fillet wrapped in nylon mesh (such as a piece of pantyhose). Tie a string to the bait bundle and lower it into the tank after the lights are out. Wait a half-hour or so and lift out the bundle with worms clinging to it. Swish them off in a bucket of freshwater and return the bait to the tank to catch another batch. Keep this up every evening until the population is under control. And keep the detritus vacuumed out of the tank.

What kind of lighting do I need to use?
If your aquarium contains no invertebrates or plants that require intense, wide spectrum illumination, almost any fluorescent lighting system will suffice. Often your dealer can suggest a particular brand of lamp that will help bring out the vivid colors of your fish. If, on the other hand, you plan to stock species that require light, such as anemones, you must give the lighting system more thought.

In this short space I cannot discuss all of the factors that must be taken into account in the design of a lighting system for photosynthetic invertebrates. Suffice it to say that many lighting systems will work, and you should carefully research the available information before choosing the lighting for your particular application.

Which tank additives should I use?
I'm not a big fan of tank additives, especially those that contain vitamins, "growth factors," or other organic components. Certain inorganic additives may prove useful, however. For fish-only tanks, chemical powders that buffer the pH and increase alkalinity may be used if your test results indicate that such action is necessary. Alternatively, you can make partial water changes more frequently.

For tanks with invertebrates and, in particular, for reef tanks, certain additives may be required to maintain proper levels of some specific ions that these organisms remove from the water continuously. Most commonly, a calcium supplement is needed to maintain the calcium concentration of the tank at about 400 ppm. Use of any calcium supplement should be predicated upon regular testing of the water for calcium.

Corals and other organisms that manufacture a calcium carbonate skeleton or shell need strontium as well as calcium. Many reef hobbyists have reported excellent growth and development of these invertebrates when a strontium supplement is used in addition to calcium. Iodine is required by soft corals, crustaceans and other invertebrates, and can be added in small amounts on a regular basis.

You cannot test for either strontium or iodine, so you must depend upon the recommendations of the supplement manufacturer for an appropriate dosing schedule. Do not rely on mixtures of "trace elements" to supply the compounds just mentioned in appropriate amounts, and make note that none of these are needed in a fish-only tank. If you think your fish need additional vitamins, add a vitamin supplement to the food, not to the tank water.

Which salt mix is the best one?
There is actually no "best" brand of salt mix. I have used all of the major brands over the years, with good results. If you are trying to limit the concentration of phosphates in your tank (see the discussion of algae control, above), select a mix that does not contain phosphates detectable with your test kit.

If you are considering switching brands, buy a bag of the new brand and mix up a batch. Allow the mix to sit overnight — preferably with aeration — to permit the salts to completely dissolve and the pH to stabilize. Then, test this batch for pH (which should be 8.3.), alkalinity (which should be 3.5 meq/l or more), calcium (should be 400 ppm or more) and phosphate (should be zero). If the mix passes these tests, use it.

What do I do in case of a power failure?
In a well-maintained marine tank that is not overcrowded, a power outage of a few hours is not usually cause for concern. If the outage extends beyond four hours, you can take the following precautions to protect your fish.

Cover the tank with a heavy quilt or blanket to retard heat loss.

Aerate the water every half-hour by dipping some out with a clean pitcher and pouring it back into the tank from a height of about one foot (30 centimeters) to agitate the water and promote gas exchange.

As soon as power is restored, check to make sure all equipment has restarted properly and plan to do a partial water change the following day.

If the outage has lasted longer than eight hours, test the tank and observe the fish carefully for problems that may develop over the next several days. If a week goes by without noticeable problems, you can rest easy.

If you live in an area that is subject to frequent power outages of long duration, you might want to consider a battery-operated air pump as a back-up, or, if your fish collection is a valuable one, an emergency generator.

How do I know if I am feeding my fish properly?
First, learn all you can about the natural diet of the fishes you intend to keep, and try to duplicate this as closely as possible in the aquarium. Second, feed as wide a variety of foods as possible. Third, experiment. Try different brands and types of foods available from your dealer. It is best to buy foods in small quantities that will be used up quickly. Each time you need food, buy a type that you have not used recently. Also, experiment with fresh seafoods and greens from the grocery store.

Providing a nutritious, varied diet is one of the easiest and least costly aspects of maintaining a marine tank. Feed your fish twice daily, and feed only what is completely consumed within a few minutes. Be sure to remove uneaten food promptly from the tank.

Can you suggest some good books on marine aquariums?
The accompanying sidebar contains a number of references that I believe should be on every marine aquarist's library shelf. As I have emphasized a number of times in this series, one of the tasks of becoming a successful, responsible marine hobbyist is to read about saltwater aquariums and the fish and invertebrates that are most likely to do well in them.

These are the top ten questions. Of course, there are more, and I don't have the answers to all of them. Read all you can, talk to fellow hobbyists and learn from your own experiences. In time, you will develop the ability to reach the right answers on your own.

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Reader Comments

Gary    Greenbank, Washington, WA

5/14/2013 5:24:57 PM

I have an Annemarie that I recently introduced to my marine tank. It is not doing well all parameters are fine. A breeding pair of yellow striped maroon clowns try to nurture it. It appears that it's clock is off if I turn the light on at night it is open and appears to be feeding. When the timer turns the light on in the day time it shrivels up and stays that way all night when it opens with the male clown sleeping in it. Water flow same at night and there is plenty of light in the day time. It stays attached, does not move. I have tried shading it nothing seems to change this behavior. What do you make of this?

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