Marine Aquariums for the Beginner

Starting a marine aquarium is a daunting project for the uneducated beginner.
When considering the available variety of tanks, filtration, substrates, salt mixes, lighting and inhabitants, options abound and choices are difficult. Nobody wants to make the ?wrong? choice, the consequences of which can cost money, headaches and loss of marine life. Prospective aquarists can consult pet store employees, books, online message forums, and many other sources, all of which may or may not provide useful and accurate information. Even when the information is correct, it is often far too advanced for the casual aquarist who wants merely to keep some interesting, colorful marine life, but does not aspire to deep or broad knowledge of marine biology.

While it is not possible for a beginner to immediately set up a maintenance-free system, some basic knowledge will put a beautiful and simple marine aquarium within the reach of most hobbyists, despite the impression created by the reams of available technical data. Only moderate knowledge and maintenance are required, if sensible choices are made. These choices will not be the same for everyone, but should correspond to the particular aquarist?s goals.


This is usually the first choice to make, because it determines the size, number and combination of animals that can be kept, and is limited by the available space allotted to it in the hobbyist?s home. The tank presents two basic choices- glass or acrylic, and drilled or not, so four combinations exist.

Glass is much heavier than acrylic, is brittle, and has a slightly greenish tint, especially in the thicker panels used in bigger tanks. Glass tanks also show a thick green line at each corner, where the pieces are butted together. This line is absent from acrylic tanks, whose front and sides are made from one piece of material that is bent to form smooth, rounded corners. Acrylic tanks are also clearer, stronger (because they have some ?give?), much lighter and usually more expensive than glass. They are also much softer than glass, which is probably their worst attribute. It is very difficult to keep an acrylic tank for any length of time, and keep it clean, without scratching it. This is particularly true in times of heavy algae growth, which is the eternal bane of the beginner. Although kits can repair these scratches, those repairs are difficult below the waterline, which is of course where most scratches occur.

While a non-drilled tank is the traditional and simple ?box of water? with which we?re all familiar, a drilled or ?reef-ready? tank carries some simple modifications. Holes, usually two or more in the tank?s bottom, allow water to flow into and out of the tank. This creates additional circulation, and allows various equipment (heater, filtration, chiller, etc.) to sit out of sight below the tank. The area around the drilled holes is enclosed by an overflow box, which stands on the bottom of the tank and reaches not quite to the top. Its top edge is serrated, forming a weir that lets water flow out of the tank only when the height of the water exceeds that of the overflow box. This design requires plumbing to connect the tank to the sump, which is a smaller container of water below the tank that holds the equipment.


The simplest, most effective and preferred method of marine aquarium filtration is protein skimming combined with live rock and sand.

Protein skimming is a means of removing dissolved organic compounds from the water. It uses a pump to force water into a column, where it mixes with millions of tiny air bubbles. The surface of the bubbles attracts these dissolved organics, just as any water surface attracts a film of contaminants, which then stick to the bubbles as they rise. When they reach the top as foam, they burst in a collection cup or chamber, in which the compounds collect and can be periodically removed.

Many types and sizes of skimmers are available, and while their price is not always indicative of their quality, effectiveness or efficiency, it is generally true that the very cheap ones are worth what they cost. Skimmers are available in hang-on and in-sump models, and in many different sizes to suit any application. If using a sump, be sure to select a model that will fit into it easily, with room left for installation, maintenance and removal.

Live rock is the basic structure for most marine aquaria, and is simply rock from a living reef. It is usually from an ocean reef, but could also come from an established reef aquarium. Though not really alive, it carries that name because it is very porous and filled with various living organisms that benefit the system via biological filtration and waste metabolization. The live rock will harbor the bacteria that convert waste ammonia to nitrate, and it can even act as a denitrifying agent to reduce the nitrate level. Although the use of live rock will help stabilize the water parameters, periodic water tests are still necessary even after the cycle?s completion. Though even scientists do not completely understand its entire benefit, tanks with one to two pounds of live rock per gallon of water are much more successful than those without it.

On the tank?s bottom will usually be a layer of sand substrate from two to four inches deep. All those grains of sand provide vastly increased surface area for biological filtration, as well as serving as home to many small life forms such as worms, small crustaceans and protozoans. The sand bed also pleases the eyes with its natural appearance, mimicking the look of a wild reef.


Because reef tanks include many photosynthetic organisms, they require much more intense lighting than do tanks housing only fish. Although the fishes? colors will brighten and deepen under reef lighting such as metal halides, power compact fluorescents or VHO (very high output) fluorescents, normal fluorescent ?shop lights? will suffice for a marine fish tank, if it does not contain corals. Using more intense lighting over a fish-only tank is mostly a matter of aesthetics. Although some corals can survive and even thrive under normal fluorescent lights, these are the minority, so the diligent hobbyist will research the lighting needs of any animal before purchasing it.


The obvious and biggest difference between freshwater and marine tanks is that marine aquaria contain salt water. The goal, which is unreachable, is to match oceanic conditions. The first step toward that is adding salt to the water. It is important to begin with pure, rather than household tap, water, which may contain problematic impurities such as phosphates, nitrates, and possibly even trace metals such as cooper or lead. The gold standard is RO (for reverse-osmosis) water, which we then combine with one of the commercially available salt mixes. A calibrated tool, either a hydrometer or refractometer, ensures the proper amount of salt by measuring the water?s specific gravity, or SG. This is a ratio of the salt water?s weight to the weight of the same amount of pure water. An SG of 1.024, for example, tells us the tank?s water is 1.024 times as heavy as the same volume of pure water. While fish can tolerate a fairly broad range of SG, reefs generally cannot, so SG is an important measurement to monitor and control.

Other relevant water parameters include pH, alkalinity, temperature, nitrate, and, in the early stages after set-up, ammonia and nitrite. The pH level indicates whether the water is acidic or basic (alkaline), and to what degree. The target is 8.2-8.4, slightly basic. Alkalinity, not to be confused with an alkaline pH measurement, reveals the water?s ability to resist forces acting to change its pH. This is important because many of the aquarium?s biological processes tend toward the acidic. Because most marine aquarium animals are native to tropical seas, the water must stay around 78-82 degrees Farenheit. A heater easily controls this parameter, and a thermometer measures it. Nitrate is the final chemical product of the bacteria?s biological filtration processes, and is not generally known to be harmful to most fishes at levels below 100 or so parts per million (ppm). Other reef animals, such as corals and other invertebrates, suffer at levels above 40-50 ppm. Periodic partial water changes, limited nutrient importation, and effective nutrient exportation (i.e., protein skimming) will effectively control nitrate levels.

Ammonia and nitrite accompany nitrate as products in the chain of biological processes. In simple terms, fish and decaying food excrete waste in the form of extremely toxic ammonia. Bacteria in the water convert this ammonia to nitrite, which is also poisonous, but much less so than ammonia. Other bacteria then convert the nitrite to nitrate, which is only slightly toxic, as described above.

The importance of this process is evident when considering the tank?s initial set-up. Because a new tank has none, or very few, of these nitrifying bacteria, any biological processes the hobbyist introduces will produce enough ammonia to kill fish. Such processes must therefore follow a waiting period, or ?cycle,? during which the beneficial bacteria establish colonies in the tank sufficient to detoxify the ammonia and resulting nitrites. After adding the water, substrate and live rock, we must therefore wait to add any fish until this cycle is complete. Now is when the ammonia, nitrite and nitrate test kits are most valuable. The live rock will harbor at least some dead and decaying organisms, which will introduce ammonia to the new tank. This will elicit rising ammonia test readings, followed by a period of falling ammonia and rising nitrite levels as the bacterial colonies grow and consume the ammonia. As still more bacteria grow and consume waste, nitrite levels fall and nitrate levels begin to rise. When the test finds no ammonia or nitrite at all, the cycle is complete. It is not until now that the tank houses enough bacteria to perform the biological filtration necessary for the fishes? health. Even after this time, fish should be added gradually, so as not to overwhelm the bacteria with too much waste and cause another ammonia spike.


During the tank?s cycle, the proactive hobbyist will not only be testing water conditions, but also researching the aquarium?s potential residents. To visit the local fish or pet store without a plan, and simply buy whatever ?looks cool,? is to invite disappointment, and possibly disaster. Marine animals are as diverse in their needs, compatibility, behaviors and ability to adapt to captivity as they are in their appearance, so to keep them successfully requires research and planning. Even after a plan is set out, failure will likely ensue unless it is followed. While the combinations of acceptable inhabitants are nearly limitless, some guidelines will prevent most problems.

It is impossible to overemphasize the importance of animal research. Buying all the right equipment, setting it up properly, and meticulously monitoring and maintaining water and food quality will not prevent frustration for the aquarist who mixes incompatible fishes, keeps species that are ill-suited for captivity, or simply overstocks his tank. Many butterflyfishes of the genus Chaetodon, for example, are known as obligate corallivores, meaning they share a specialized diet of live coral polyps (Michael, 2001). Because this diet is unavailable to them in the home aquarium, most will waste away and die there, however beautiful they were in the store?s display tank. Even hardy species that typically thrive in captivity can disappoint us if they lack proper tankmates. Housing a triggerfish from the genus Rhinecanthus, for instance, with a small firefish or flasher wrasse is to sentence the latter pair to a nearly certain death, even though they would otherwise flourish. And we?ve all seen the laughable fish densities achieved in small store tanks, which work only because the fishes don?t remain there indefinitely, but only until they?re bought. Because our own tanks are long-term affairs, we need to try to match the stocking density of the wild reef.


Patience is probably the single most important virtue for the marine aquarist. An old reefkeepers? saying tells us that only bad things happen quickly in a reef tank. The corollary is that the good things must happen slowly. Often in the excitement borne of weeks or months of research, study, consideration and shopping, the beginning hobbyist rushes to fill his new tank with animals, or makes an impulse buy. After viewing beautiful, mature reefs for so long, a new, lightly-stocked tank can seem drab and even stark in comparison, but living with that for a short time, while slowly adding animals, is infinitely preferable to rushing toward completion too quickly and losing animals. Even after the tank is functioning properly and its life is thriving, it can slide downhill quickly if not maintained, but this maintenance tends to lessen as time passes. Indeed, part of the beauty of a marine aquarium is that it tends toward stability as it ages, while still revealing something new at every turn. It can fascinate us forever, and is truly a life-changing hobby.