One of the most visually interesting aquarium ecosystems you can establish is a marine reef aquarium. These saltwater aquariums require time, dedication, and some expertise, so they are not recommended for beginners. However, if you’re at least somewhat familiar with keeping aquariums and know that you enjoy the hobby (and can bear the expense), then a reef aquarium might be your next step.

There are a number of decisions you’ll need to make as you get started. First, where in your house will you want to position your aquarium? It should be easily viewable by your family and guests, but should not be located in a high-traffic area of your house. Also, the aquarium should not be positioned in an area where there are drastic temperature fluctuations, such as a drafty area near a window, near a radiator or other heat source, in direct sunlight, or in the kitchen (where cooking routinely causes spikes in room temperature). You will want the water temperature in your tank to remain as constant as possible.

You will want the largest tank you can manage, that will fit in your space. For reef aquariums, large tanks (such as 200-gallon tanks) will provide a more stable environment, as the water temperature and chemistry will be easier to maintain. In smaller tanks, the introduction of new tank elements can quickly cause drastic fluctuations in water chemistry; in large tanks, the effects of such new elements have more volume through which to disperse.

Acrylic versus glass is another important decision. Glass is heavier, but is generally preferred for all but the largest tanks. Glass is much more difficult to scratch than acrylic, and also maintains its clarity (some types of acrylic will yellow with age). However, acrylic is less distorting, can be molded into a variety of shapes, and is more shock resistant. A shallower tank, 24 to 30 inches, is usually a good choice; shallow tanks provide better depth of view for your reef and marine life, providing a more natural look and better light penetration.

Many reef aquariums are set up with a sump, which is simply an accessory tank that sits underneath your main tank, where equipment such as filtration devices and heaters are set up. A sump allows for clutter-free presentation in your main tank; it also allows for greater overall water volume in your reef environment, rendering the water less susceptible to fluctuations in salinity and pH. Through the use of a simple pump, water is fed from your main tank through PVC piping into the sump, and is then returned via another pipe. Many tanks are sold as “reef-ready” or “pre-drilled,” meaning simply that they already have holes pre-drilled into the back of the tank for the PVC piping leading to and from the sump.

Many factors go into determining the lighting you’ll need for your reef tank, but as a general rule, you should figure on 8 watts of lighting power per gallon of water. Your lighting not only provides a better viewing experience but also is necessary for photosynthesis to occur in your coral and plant life. Most aquarium owners use a bluish, “cooler” light, above a measure of 10,000 Kelvin; metal halide lamps are very effective, as well as bulbs that produce “actinic” light. However, the heavy blue cast may seem unnatural, so you might experiment mixing these cooler bulbs with a broader-spectrum bulb, measuring 5,500 Kelvin, to add some warmer color tones.

Most reef aquariums and other saltwater tanks are filtered with protein skimmers. This filtration unit injects air bubbles into the tank, creating a foam similar to sea foam. Organic molecules collect in this foam, which is then captured in a collection cup. This method of filtration removes dissolved organic compounds before they break down into ammonia and nitrites. The protein skimmer is usually set up in the sump tank, underneath your main tank. Often, protein skimmers are underrated for the size of the tank, so if you are setting up a large tank, be sure you have enough filtration power. And avoid simple canister filters; while effective for freshwater aquariums, canister filters are usually not adequate for reef tanks.

Other equipment you will need to purchase for your reef tank include heating units (to be placed in the sump tank), which should be adequate to maintain a constant temperature in your tank. Reef ecosystems usually require warmer water than other kinds of aquarium environments, so you may need a powerful heating unit to keep your water comfortable for your marine life. (The high intensity lighting for your tank will provide some heat as well.) Also, the sump tank will need a pump to feed water back into your main tank, and your main tank should be outfitted with one or more powerheads, which create underwater currents, helping to circulate waste out of your tank and nutrients toward your coral and other stationary invertebrates.

Once your equipment is in place, you are ready to fill your tank with water. Most tank owners use reverse osmosis de-ionized water (RO water), available at aquarium stores; don’t use plain tap water, as it contains too many chemicals. Mix marine salt (also available at your aquarium store) with your water before adding it to the tank, about a half cup of salt per gallon of water. As water evaporates from your tank over time, you only need to add more water, not salt: the salt does not evaporate, so adding more salt would increase the salinity.

Finally, add your substrate layer -- usually sand, at a depth of 4 inches or so. And wait for your tank’s chemistry and temperature to stabilize, a process that might take several weeks. Salinity should be stable at 1.023 to 1.026. Cleaning creatures such as snails and crabs would be next, and then your reef fish. Most aquarium keepers recommend not adding coral or anemones until your tank is a few months old. Then you can begin enjoying the fruits of your labor.