Successful Marine Aquarium

Realistic information about setting up and maintaining a successful saltwater aquarium.

I might as well tell you this right up front. You’ll find out sooner or later anyway. The “secrets” mentioned in the title aren’t really secrets at all. You can find the same information in many different books and magazine articles, but at least here they’re all in one place. I called them secrets because I read somewhere that if you use the word secrets in the title, more people will read the article. Also, there are really 10 topics — five in this article and five in the next one — not just seven. I guess I could have called it “Ten Tips To A Thrifty, Thrilling, Triumphant Marine Aquarium,” but I like the alliteration of “Seven Secrets” better, so I’ll just claim literary license on the title and we’ll move on.

I’m writing this for those aquarists or potential aquarists who would like to go marine, but have reservations. The techniques and technology of marine aquarium systems have taken giant strides in the last five years or so, and it is very easy to get the idea that one has to know all about redox potential, ozonation and carbonate hardness, and invest a lot of money in live rock, trickle filters, metal halide lights and denitrifying filters before one can be a marine aquarist. This is not so. Now, I’m not knocking high tech systems, not at all. The new horizons that have developed in marine systems for hobbyists are truly exciting, and fantastic things are now possible. But one can still start small and simple (and stay small and simple), have a lot of fun and learn a great deal without spending large sums of money.

I’ve made six assumptions about what you want in a first marine aquarium — three are positive and three negative.

The Negative Assumptions

1. You don’t want to spend a ton of money

2. You don’t want to devote a whole room to a marine aquarium

3. You don’t want a high tech system with a maze of tubes, pipes, filters and pumps (at least not yet)

The Positive Assumptions

1. You want to run a successful marine aquarium the first time you try

2. you want to learn first hand what really makes a marine aquarium work

3. you want an interesting and attractive marine display

With a little knowledge and patience, it’s very possible to create a beautiful and fascinating marine aquarium without spending much more than one would on a freshwater tank. If funding is really tight, it’s possible to make much of the required equipment from things that can be purchased at hardware and building supply stores. Such a pick-up, pieced-together system, of course, will never look as good as one built from equipment designed and constructed especially for marine aquariums, but it can support marine life just as successfully.

A simple, inexpensive marine aquarium system can function very well, but it is important for the aquarist to know about all the essential elements of the system and to understand how they function. With this basic knowledge, one can keep marine fish alive in gallon jars. Without this knowledge, it’s failure city.

Secret One: The Tank
The tank should be all glass, fitted together with a silicone cement. If you build your own tank, make sure that the silicone cement you use is made especially for aquarium fabrication. Some silicone cements contain compounds that inhibit mildew growth, which is great around bathtubs and windows but can cause serious problems in aquariums. (This is also a good thing to know when you want to fix a leaking tank.) Tanks can also be made of plywood, fiberglass or cement, but these materials pose special problems, and the beginning marine aquarist is wise to avoid them. All-glass tanks are relatively inexpensive, so it is usually better to buy rather than build one.

There are often bargains to be had in used tanks. Clean a used tank well, but don’t use special cleaners or detergents. A little well-diluted bleach and a lot of scrubbing and rinsing is best. A 20-gallon tank is a good compromise between size and expense for a marine tank. One can go to 50 gallons with a little more money, but the cost of everything climbs sharply past 40 to 50 gallons. A beautiful marine display can even be set up in a 10-gallon tank. The real secret to successful, tiny marine tanks is to keep very few fish and/or invertebrates in them.

Be sure the tank is on a sturdy stand or table. Saltwater is heavy (1 gallon weighs about 8½ pounds), and a full tank that drops to the floor can ruin one’s day.

A glass cover (or a specially made plastic tank hood) that sets down below the upper edges of the tank is important. Water accumulates on the underside of the cover and drips back into the tank. If the cover just sits on top of the tank, water flows to the edge of the cover, creeps between the cover and the tank and then runs down the side of the tank, leaving a thick, salt-crust trail as it evaporates.

Secret Two: The Water
Obviously, to run a marine tank, one needs saltwater. If you live in a coastal area, you can use natural seawater. Seawater is basically the same all over the world, so even if you live on a northern coast, natural seawater can be used for tropical marine organisms. The water must be of the proper salinity and be free of pollution. Using natural seawater is more involved than using artificial sea salts. Although natural seawater itself is basically free, one must still collect it, filter it, purify it if necessary and store it.

Major brands of artificial sea salts are now so well compounded that they support even the most delicate types of marine life. Perhaps the worst thing about artificial sea salts is that they are usually made up with city tap water. Tap water these days contains chlorine andor chloramine (and who knows what else). As when using tap water for a freshwater tank, these compounds must be removed before a sea salt mix is added. Although artificial sea salts are far more convenient and pollution free than most natural seawater, the freshwater source used to mix up the sea salts must be processed if necessary. Passing the water through an activated carbon filter before adding the salt mix is always a good idea.

Salinity is a measure of how much salt is in the water. The standard measure is in parts per thousand (ppt). Seawater usually has about 28 to 35 parts of salt per 1000 parts of water. As the salt content of water increases, the weight and density of the water also increase. Increased density makes an object float higher. Thus, changes in density can be easily measured as specific gravity with a hydrometer, which floats in the water. The specific gravity of pure water is 1.0000.

Most marine aquarists refer to the salinity of their water in terms of specific gravity, the direct reading on a hydrometer. The true specific gravity of seawater in the 28 to 35 ppt range is 1.0206 to 1.0260, and most marine aquarium systems fall into this range.

It is good to keep the salinity of a marine aquarium a bit lower than ”normal” seawater. If an old-hand marine aquarist says that he keeps his systems at a salinity of 22, this is short speak for a specific gravity of 1.0220, not 22 ppt — 1.0220 is actually a salinity of 34 ppt at 80 degrees Fahrenheit when measured with a conventionally calibrated hydrometer. A little lower salinity — 1.0210 (at 80 degrees Fahrenheit) or a salinity of 32 ppt — reduces stress on the fish and keeps the tank in the proper range even when salinity increases a bit due to water evaporation. Never add saltwater to a marine aquarium to make up for water lost to evaporation. Only pure water leaves the system; the salt stays behind.

Secret Three: Biological Filtration
There are three basic types of filtration: biological, mechanical and chemical. Mechanical filtration removes particles (large and small) from the aquarium water. Water is pumped through a pad or wad of floss or other filter media, where the particles are trapped. The filtering media is then cleaned or discarded after a week or two to prevent the accumulated particles from clogging the media and reducing the flow of water through the filter.

Biological filtration is the cornerstone of a marine aquarium. If an aquarist does not understand and properly utilize the process of biological filtration, a marine aquarium will forever be a thing of mystery controlled by supernatural forces.

Marine animals and organic decay produce waste nitrogen in the form of ammonia. Ammonia is toxic to marine animals, and many fish and invertebrates become sick and die if ammonia is present in the tank water. Certain bacteria convert ammonia to nitrite. Nitrite is also toxic. Another species of bacteria converts nitrite to nitrate. Nitrate is relatively nontoxic and can accumulate to some extent (up to 100 parts per million — ppm) in the tank water without noticeably affecting most fish, although some invertebrates are not happy at concentrations of nitrate above 15 to 20 ppm. Note that many corals do not do well at nitrate levels above 5 to 8 ppm.

It takes from three to six weeks for the bacterial colonies to develop in a biological filter. After the tank is set up, a few hardy fish or a crab or two are put in the tank to create a source of ammonia to get the bacterial colonies started. The best and simplest way for an aquarist to tell when the tank is “broken in” is to test for nitrite. When the nitrite level drops to between 0 and 5 ppm, the bacteria colonies are established and other fish can be placed in the tank. The nitrite test is simple and available from most aquarium stores. If nitrite testing is not done, an aquarist can usually assume that the cycle is complete after six weeks.

A biological filter must do just one thing. It must contain a media with a large surface area for bacterial colonies to grow on, and allow a flow of oxygen-rich water containing the waste nitrogen compounds to pass freely over and through the media.

Depending on its design, a biological filter does other things as well. In the form of a trickle filter, it provides efficient biological filtration and it also provides excellent gas exchange, removing carbon dioxide from the water and replacing oxygen in the water that has been consumed by the nitrifying bacteria and by the metabolism of the animals inhabiting the tank. In the form of an undergravel filter, it provides less efficient biological filtration but also functions as a mechanical filter, trapping detritus and food and waste particles, where other bacteria break them down to the basic minerals.

A well-designed trickle filter is an effective biological filter for small and large marine aquariums, but a trickle filter requires an external (usually under the tank) installation, and this increases the cost and complexity of the system. An undergravel filter is installed within the tank, and although it requires more maintenance than a trickle filter, this “traditional” type of biological filter does a very good job on a small marine aquarium.

An undergravel filter consists of a plate with fine slits or holes that rests about ½-inch above the tank bottom. A layer of filter media rests on this plate, forming the bottom surface of the tank. One to four large-diameter tubes extend upward from the area under the filter plate to near the surface of the water. Water is drawn from under the filter plate up to the surface of the water, circulates through the tank and then cycles again through the filter media on the tank bottom. Air released at the bottom of the tubes will power the water cycle, and this is quite adequate for small tanks. However, powerheads (small electric pumps that sit on top of the filter lift tubes) move much more water through the undergravel filter and should be used on large tanks.

There are three major factors to consider in the structure of an undergravel filter: particle composition, particle size and thickness of the filter bed. The larger the particle size, the less the media surface area, the greater the water flow through the filter and the thicker the filter bed must be. The finer the particle size, the greater the media surface area, the slower the water flow through the media and the thinner the filter bed can be.

A coral gravel filter with particles about 1/8-inch in diameter or slightly smaller should be at least 1½ to 2 inches thick, whereas a silica sand (coarse sandblasting sand) filter with much smaller particles need only be about ¾ to 1 inch thick in a small aquarium. Silica sand does an excellent job in a small aquarium, and with proper water changes, pH levels remain very stable within the proper range.

The optimum range for pH in a marine tank is around 8.2, although it can drop to 7.8 without causing severe distress to most fish and invertebrates. The control of pH is in the buffer system of seawater, not in a calcareous filter media. The &”secrets” to keeping the pH in the proper range in a small aquarium include not overcrowding the aquarium, not overfeeding the animals and making regular water changes.

Many aquarists also use a protein skimmer to remove dissolved organics before they are broken down by the biological filter. This helps reduce the amount of nitrates that accumulate in the tank water. If there is a lot of live rock in a marine aquarium, neither a trickle filter nor undergravel filter is neeed — just a large, efficient protein skimmer. The live rock has so much surface area that it can provide all of the needed biological filtration.

Secret Four: Chemical Filtration
Chemical filtration consists of passing water through a filter containing activated carbon and/or a resin media. Both have microscopic pores that capture organic and other molecules and remove them from the water. The carbon is depleted when the pores are filled with organic molecules that are removed from the water.

Activated carbon is very effective at removing the organic dyes that discolor aquarium water. A good marine aquarist makes good use of both mechanical and chemical filtration and changes the media in these filters at regular intervals. Some aquarists don’t use carbon all the time because it may remove important trace elements, so they run carbon perhaps one week per month, just before doing a water change.

A simple external filter that hangs outside on the end or back of the aquarium does an excellent job of mechanical and chemical filtration on a small marine aquarium. A simple inside corner filter (the type used for freshwater tanks) loaded with floss and activated carbon also works well.

Although a lightly loaded marine aquarium can be run successfully without an auxiliary filter, such a filter greatly improves water quality and clarity. Activated carbon lasts for some months before it must be changed. It can be changed every four to six months or changed when the water develops a slight yellowish color. A strip of white plastic with a very light yellow mark on it can be an indicator of water color. If the yellow mark is not distinguishable from the front of the tank when the plastic strip is placed in the water at the back of the tank, then the carbon needs changing.

The best activated carbon for marine aquarium use is in the form of small granules about the size of a pinhead. Dust is minimal and a hissing sound may be heard when the dry carbon is immersed in water. A carbon and/or resin filter is most effective when water flow is directed through the media rather then allowed to flow around it.

In the second part of this article, I’ll look at five more “secrets” to a successful, simple marine aquarium. Temperature, lighting, fish selection, foods and feeding and what to do about the most common parasite problem a marine aquarist encounters are all included.

Keeping a successful marine aquarium of any size or complexity is mostly knowledge, observation and maintenance. Sure, a big tank with expensive equipment allows an aquarist to keep a greater abundance of marine organisms, including many that require coral reef water quality and lighting almost like natural sunlight. On the other hand, a 20-gallon tank doesn’t require too much maintenance, either, and as long as one knows the limitations of a small, simple marine aquarium, many species of marine fish and invertebrates can thrive and grow in a simple little aquarium far from the sea.

A simple, undergravel-filtered, marine aquarium setup can be made from construction materials obtained at hardware and building supply stores or from equipment designed for marine aquariums and sold in aquarium stores. A tank as small as 5 gallons, built and operated in the “traditional” marine method, can support a few saltwater organisms, and 30- to 75-gallon tanks set up the same way can support many more. These tanks will not be as low in maintenance or support as great a number and variety of organisms as a tank established with a high-capacity protein skimmer and high intensity lighting, but these simple setups still works very well as a low-cost introduction to the fascinating world of marine aquarium keeping.

The four topics in the first half of this article — tanks, water, biological filtration and chemical filtration — and the six in this half will help a developing marine aquarist understand the basics. A small, uncomplicated marine aquarium setup is an excellent way to learn the nuts and bolts of the hobby.

Secret Five: Water Management
A water change can be considered a type of filtration, because you are removing accumulated dissolved organic compounds, as well as adding trace elements that have been depleted. In a typical small aquarium, a 10- to 20-percent water change per month is about right. An aquarium with a heavy biological load may require more, and a light biological load may do well with less. Weekly water changes of 5 percent are even better because the smaller, more frequent changes create less stress on the fish and invertebrates.

The saltwater should be made up about a day before the actual change because this allows time for all elements in the salt to completely dissolve and “stabilize.” Changing small amounts of water in small marine aquariums is not difficult and is one of the greatest “secrets” to a successful, small and simple marine aquarium.

Water movement in the aquarium is also of critical importance. A slow cycling of water around the aquarium and through the filter may keep everything alive, but carbon dioxide can easily accumulate to dangerous levels with such slow water movement, especially if algae growth is limited. Most oxygen/carbon dioxide exchange takes place at the surface of the water, so it is important to provide a strong turnover of tank water from bottom to top. An airstone or two placed in the tank will provide this turnover, as well as increase the turbulence of the tank water, which increases the rate of exchange of oxygen and carbon dioxide.

Secret Six: Temperature
There are two important considerations about temperature. First, a marine tank should always be within the range of 75 to 85 degrees Fahrenheit. Many tropical marine fish and invertebrates are stressed if temperatures go below or above this range, and many die if the temperature dips below 70 or above 90 degrees. Second, the temperature should not change with great rapidity. For example, suppose the aquarium heater ceases to work and you find the tank at 66 degrees Fahrenheit one morning. Many or all the fish may well survive if the temperature is increased to 75 or 80 degrees over a period of a couple of hours, but moving them immediately into 80-degree water may well cause immediate death.

Most marine aquariums, small and large, require a heater all or part of the year. Make it a point to be aware of how the heater is functioning. Keep a small thermometer in the tank and check it frequently. Watch the little light on the heater. Make sure it goes on and off when the room is cooler than the tank. If it stays on all the time, the heater may be broken or it may be too small for the tank. If it never comes on, it may be broken or set too low.

Now here’s a tip that may make reading this whole article worthwhile. Make sure that the heater is unplugged when water changes are made or whenever the water level in the tank is lowered. If the glass tube on the heater is exposed to the air and the heater turns on, the glass tube may well overheat and crack, and expose the electric elements in the heater to saltwater. Trust me, you don’t want this to happen. It can cause an electrifying experience.

Secret Seven: Lighting
Lighting is very important with a tropical marine aquarium. It is far more important to have proper lighting in a marine tank than in a freshwater tank. Freshwater fish often live in dark waters and shaded areas where light levels are low and variable, whereas marine tropical fish and invertebrates typically come from relatively shallow, clear tropical seas where sunlight is bright and intense all day long.

The best light for a marine aquarium, and essential for systems in which algae and coral are grown, is very bright and has strong peaks in the violet/blue and orange/red parts of the spectrum. An ordinary 2- or 4-foot shop light fixture with two daylight or full-spectrum fluorescent tubes provides enough light for most low-cost, traditional marine aquarium setups. Such a setup is not adequate for most corals and other photosynthetic animals, but is far better than the single small bulb provided with many light hoods designed for freshwater use.

Many marine fish can be kept under such low-light conditions, but chose the fish carefully. Pick fish that normally live in deep water or spend the day in caves or under ledges. These species require less intense lighting. Steer away from tangs and angelfish and other species that need the high light levels of the reef tops. Many crustaceans, shrimp and crabs also do well under low-light conditions.

Secret Eight: Animal Selection
Keeping a marine aquarium is far easier if one starts with strong, healthy specimens. Look for fish with clear eyes, a full round abdomen and clear, full fins. Avoid fish with sunken abdomens, missing scales, blotchy skin and ragged fins. Behavior should be alert and aware. There should be a strong interest in food and feeding, except if the fish has just fed. A slow-swimming fish with its head pointed up and little interest in its environment or in feeding seldom survives for long.

Crustaceans should have all their appendages, and their color should be clear and normal. Most crustaceans prefer the cover of reef structures. One that sits in the open and has little reaction to stimuli is to be avoided. A combination of fish and invertebrates in the same tank is more difficult to maintain than just fish or invertebrates, but once a combination tank is established, the result is very interesting. Be sure that there are plenty of hiding places for shrimp and crabs.

Secret Nine: Disease and Quarantine
After problems with “new tank syndrome” (high ammonia and nitrite levels) and the lack of proper water changes, parasite disease is the next greatest cause of defeat and distress among marine aquarists. Disease diagnosis and cure is a complex topic, and I refer you to my book, The Marine Aquarium Handbook: Beginner to Breeder, for more complete information. But I can provide a few tips here.

The most common and most destructive parasite that plagues marine aquariums is Amyloodinium ocellatum. This is a dinoflagellate parasite of marine fishes that reproduces rapidly and can easily complete its life cycle in a marine aquarium. Although there are many other types of bacterial and parasitic diseases that affect marine aquarium fish, this is the biggie. If most or many of your fish die over a period of several days to a week, the most probable cause is an infestation of this parasite.

A heavily infected fish will be covered with numerous very tiny white specks on the sides and fins. Lightly infected fish often scratch, rub or flick themselves against the substrate or reef structures in the tank. Heavily infected fish respire rapidly, lie on their sides on the bottom or hide in the reef structure and show no interest in feeding. If any of your fish have this parasite, the entire tank must be treated.

There are three basic life stages of this parasite. The first is a free-swimming, microscopic dinospore that lives for one to two days and must find a fish host or die. The second is a small cyst that lives for several days in the gills or on sides and fins of a fish. The third is a larger cyst that drops from the fish and completes development on the bottom of the tank over a period of one to four weeks. A couple of hundred dinospores can be released from the resting cyst on the tank bottom, and they then infest other fish in the tank.

A copper level of 0.15 to 0.2 parts per million in the tank water will kill the dinospore, so continuously maintaining this level of copper in the tank water for three to five weeks will remove this parasite from the tank. Copper levels must be checked every day, especially during the first week of treatment, because some copper compounds precipitate quickly from the water in a tank that has never been treated with copper. A single copper treatment is often gone from the water in about 24 hours and the tank is then unprotected from the parasite.

The standard treatment if you have only a single marine tank is to give infected fish a 1-minute freshwater bath (make sure there is no chlorine in the freshwater and that water temperature in tank and bath are about the same). The immediate switch to freshwater causes the cysts to drop off the fish. The fish are then returned to the tank and the proper copper level is kept in the tank water for at least four weeks. The cysts that drop off the fish in the freshwater bath are still alive, so this water must not be added to the tank. Copper in the water also kills other invertebrates, especially corals and anemones, so these animals cannot be kept in a tank treated with copper.

An alternative method for removing these parasites from a tank is to keep the tank free of fish and at a high temperature (83 to 86 degrees Fahrenheit) for at least six weeks. The cysts on the bottom all hatch, the dinospores die without finding a host fish and the tank is then free of the Amyloodinium parasite.

A marine aquarist can avoid a great deal of weeping and wailing and gnashing of teeth through use of a quarantine system. This consists of a small, 10- to 20-gallon, fully functional marine tank. Newly acquired fish are given a freshwater bath and placed in the quarantine tank for several weeks. Here they are watched for disease and parasites, treated if necessary and are given a chance to acclimate to captivity and to the particular diet choices provided by the aquarist. After three to four weeks of disease-free acclimation, the fish is placed in the main display tank with at least some assurance that it is not carrying disease or parasites into the tank.

Secret Ten: Food and Feeding
If you intend to set up a low-cost marine aquarium and feed your fish nothing but an inexpensive flake food, I have two words of advice: forget it. A high-quality, marine fish flake food is good for fish and invertebrates, but even the best flake food should not be the only food. Most marine fish feed on a variety of organisms in nature, and many fish and invertebrates include various types of algae in their diet.

There are a number of different types of frozen foods available these days for marine fish and invertebrates. These are made from marine food sources that provide close to a natural diet for many marine animals. Also, it is very easy for a marine aquarist to get shrimp, oysters, fish, squid and other marine food organisms from the supermarket and make up a homemade food mix for marine fish. If marine algae are not available for inclusion in the food mix, use a little spinach or romaine lettuce to provide the necessary vegetable matter.

It’s not difficult to put these ingredients into a blender and then freeze the mix in ice cube trays. There are many recipes available in a number of books and articles. Even if you don’t make a mix from a variety of ingredients, freeze some raw, peeled shrimp and grate a spoonful or two for the fish every other day or so. The inclusion of this fresh food will greatly improve the quality of life of your fish and invertebrates.

Feed at the same time each day if possible. Do not overfeed. A few small feedings are much preferred over one large feeding. Pay attention to your fish during feeding times. Careful observation will tell you when they have had enough for one feeding, and then you will have a good idea of how much to feed at any one time.

Feeding more than they can eat only wastes food and pollutes the tank. Remove uneaten food from the aquarium whenever possible. A length of rigid air line tubing works well to remove small bits of uneaten food. Put your thumb over the end of the tube, extend the air-filled tube into the tank and place the end near the food particle. When you take your thumb off the other end, the food will be sucked up into the tube. Replace your thumb over the end of the tube and remove the tube containing a small amount of water and the food particles from the tank. (I know, I know, everybody knows how to do that, but just in case you didn’t, you do now.)


Article Categories:
Fish · Saltwater Fish