Tank dimensions are determined by the individuals inside your aquarium. Some fish require swimming space, and the length of the tank may be important. Some corals require intense light, and the height of the tank may be important. Some plants grow like bushes, and the width of the tank may be important. Also, the surface area of the bottom influences how much substrate and lighting you will need. Finally, the volume of the tank determines the flow rate through the circulation systems and filtration systems.
Choose lamps based upon the luminosity (lumens), the color (spectra), and power (watts). The best choice for your lighting will match the needs of any photosynthetic individuals’ spectra, provide the most luminosity, and consume the least power. Both fluorescent and metal halide lamps excite electrons bound to certain chemicals. When these electrons relax, the lamp emits light of distinct wavelengths. There are very few options for these chemicals. As a result, most lamps contain varying amounts of the same chemicals.
Fluorescent tubes emit light from the surface of a long cylinder. Avoid spirals or other strange shapes when purchasing a fluorescent lamp. Choose parabolic reflectors designed for lamps of your radius. Compact fluorescent lamps will never work as well as the equivalent straight tubes. Metal halide lamps emit light from a line source, which in turn excites a small cylinder to emit light. Because of this complexity, reflectors are designed for very specific metal halide lamps types. If possible, decide upon a particular lamp make and model and then choose the best reflector for that lamp.
All lamps are designed to operate at specific temperature. Achieving this may involve adding ventilation to your lighting or purchasing a chiller. If all else fails, you may try redirecting your HVAC to supply air, return air, or both.
As to date, the most efficient lighting available is german made T5 fluorescent lamps under parabolic reflectors. The spectra are also very impressive. American LED manufacturers have made leaps and bounds, with the introduction of new designs that come within 15% of the efficiency of T5 lamps in 2006. LEDs are rarely chosen because of high initial costs; however, long run costs of LED systems are significantly lower.
Metal halides are an attractive option for reef aquariums because they are almost a point source. If you disturb the water’s surface, then a metal halide will sparkle, similar to how sunlight appears on the bottom of a pool on a bright, windy day. Keep in mind that only the light from the metal halide will sparkle, and choose your color spectrum accordingly if you also will use fluorescent lamps.
Mechanical filters remove material from the water column by physically separating the material from the rest of the water. This separation allows easy removal of this material. There are several methods of mechanical filtration: sudden decreases in the linear velocity of water as the flow passes a drain, trapping the material in another, inert material, or foam fractionation (protein skimmer). Mechanical filters can easily be automated to minimize maintenance.
Chemical filters either selectively partition chemicals onto a surface or react with chemicals in the water column. Chemical filtration requires regular replacing or recharging of media.
Biological filtration is, in essence an integration of chemical and mechanical filtration via individuals within your aquarium, or connected to the aquarium through plumbing.
Protein skimmers are best suited for fish only tanks. Natural reefs rely on tiny particles and individuals to increase biomass. Protein skimmers are extremely efficient at removing tiny particles from the water column. As such, protein skimmers often starve a reef aquarium.
UV sterilizers are work horses in many setups. They really belong under lighting, but are considered filters by most. UV sterilizers destroy some of the nucleic acids that pass through. If enough nucleic acids are destroyed, then the individual cannot reproduce and is sterile. Use UV sterilizers with care, as they can do more harm than good.
Circulation and Aeration
The water in the aquarium can be thought of as two systems: the bulk and the surface. Water circulation is best accomplished with external pumps. Placing electric motors inside the water column also places electric fields inside the water column, which can distress a large number of individuals.
To achieve similar water quality throughout the aquarium requires proper circulation. Not only is volumetric flow (GPH, LPH) important, but the linear velocity (mph, m/s) of flow is also important. The velocity of water determines what reaches your filter in the first place, and individuals within the aquarium experience linear velocity, not volumetric flow. Choose pumps on the inside diameter of the suction and pressure side, the power (watts), and the volumetric flow (GPH). Be careful, different manufacturers may report their numbers in different units or at different head heights. I’ve found that each manufacturer has several basic designs that they scale their models from. From each line, a single model will perform most efficiently. Rarely will each model in a line outperform all models in a competing line.
Reef aquariums often require pulse flow. Placing a mechanical device in line can change the direction and/or intensity of circulation. Programmable devices can fine tune the on/off cycles to your liking, but ensure you purchase a pump that is designed for frequent stopping and starting.
The surface provides gas exchange with the surroundings. If the surface of the water is not turned over, then undesirable individuals may grow thin colonies on the surface of the water. These colonies may inhibit gas exchange and block lighting to the rest of the aquarium. Make sure you have something that only filters the surface of the water called an overflow.
Aeration may be achieved entirely with good air flow over a clean surface of water. If photosynthesis increases the partial pressure of oxygen above that of the surroundings, then aeration may not be required. In such cases, separating the aquarium from the surrounding air may improve the water quality.
An unsealed aquarium exchanges all gases including water with the surroundings. Individuals in the water and owner dosing impart a concentration gradient upon a number of chemicals within the water. Blowing or sucking air across the surface of the water will decrease this concentration gradient. Increased evaporation will also cool water.
Ventilation offers an economic opportunity to dose an aquarium. Evaporation removes only water, but leaves the dissolved chemicals behind The evaporated water can be replaced by water high in nutrients for plants or a reef. By increasing the evaporation rate, the maximum rate of dosing is also increased.
The substrate at the bottom of the aquarium can serve many purpose other than aesthetics. In planted aquariums, the substrate provides rooted plants with chemicals not available to individuals in the water column. If you have an undergravel filter, then the substrate doubles as a filter media. If you do not have an undergravel filter, then the electrochemistry of ion exchange changes dramatically with deeper substrates. Because of this, many chemical reactions take place which would not take place if water circulated through the substrate. For example, iron uptake by plant roots becomes easier, but so does the production of methane. In a reef aquarium, the substrate may become a host to a variety of individuals and acts as biological filtration. Similarly, care must be taken in a reef aquarium as deep sand beds have very low reduction-oxidation potentials. Very scary chemistry can build up and release all at once.
Oxygen is the most important molecule in water. Proper aeration, photosynthetic individuals, compressed gas, or ozone generators may be employed to elevate oxygen levels. The last two methods can overdose with oxygen or ozone and elevate the reduction-oxidation potential too much, essentially rusting individuals in your tank. Ensure that if a control system fails then the maximum dosage rate will not be toxic.
Carbon comes in many forms. Plants need carbon to thrive. The simplest type of carbon added to aquariums is carbon dioxide. Many people buy pressurized CO2 in cylinders, culture yeast to ferment, or make it electrochemically, then plumb this to the circulation system. A few plants actually use bicarbonate instead of carbonic acid, which means you can actually fertilize with baking soda. Another option is to overstock the tank with fish, who will provide an abundance of CO2. This option requires a hefty filter and more frequent water changes. Reef aquariums often use carbon dioxide to elevate calcium levels in reactors. This addition must be offset to avoid low pH, and magnesium sulfate is an attractive option. Elevated carbonate concentration (with calcium) in a reef allows individuals to precipitate calcium carbonate, a necessity of many individuals. Adequate turnover of the water, ventilation, protein skimming, and surface disturbances decrease the difference between carbon dioxide pressure in the air and in the water.
Nitrogen is essential for every aquarium. Ultimately, nitrogen is important to make proteins, nucleic acids, and other biomolecules. The source may be an amino acid or a nitrogenous base, but more than likely it is either reduced or oxidized nitrogen. Common reduced nitrogen compounds are ammonia, ammonium, and urea. Reduced nitrogen should be kept at low levels. Oxidized nitrogen is commonly referred to nitrites and nitrates, but most test kits fortunately measure other chemicals as well. Nitrogen should be present in your aquarium’s water in at least one form. Potassium nitrate is an extremely economic option. Biological filters, quality protein skimmers, and chemical absorbants are effective at removing nitrogen almost entirely from the water colony.
Calcium is important to all aquatic life. Quality plant fertilizers will ensure planted aquariums have plenty of calcium. For a reef aquarium, calcium is quickly consumed. Calcium reactors are effective at maintaining calcium in the water column, but pH must be offset as discussed under carbon. Calcium chloride does not affect pH, and chloride is reef safe. Saturating top off water with a mixture of calcium chloride and calcium carbonate should maintain both calcium and carbonate levels. Calcium salts can precipitate in the water column and test should be performed before adding calcium to the aquarium.
Potassium is the single most overlooked chemical in a planted aquarium. Plants must either take in new potassium of destroy old tissue to continue growing. There are no known negative issues with elevated potassium.
Iron is a tricky one. Iron may be the oldest chemical of life, and cells use iron to maintain the proper reduction-oxidation potential. Iron exists in two states in the aquarium: Fe(II) is missing two electrons and Fe(III) is missing three electrons. Fe(III) is not readily water soluble, so individuals must usually add an electron to Fe(III) before placing it into service. Adding electrons becomes easier as the reduction-oxidation potential decreases. For many planted aquariums, the substrate serves largely for cation exchange between the water and the plants’ roots to aid in iron metabolism. Anything from (perfume free) kitty litter to expensive substrates taylor made and color matched will work, depending on your standards of aesthetics. UV sterilizers quickly remove all iron from the water column.
Magnesium in water is depleted slowly by reefs and is essential to a reef’s growth. Buying a calcium additive with magnesium may be enough, or you can buy magnesium chloride which is readily soluble in water or magnesium sulfate.
Iodide and strontium are extremely important for most invertebrates, especially reef invertebrates. Typical levels are very low. Concentrations can be maintained by comprehensive additives or by buying plant cell culture tested compounds in bulk.
Phosphate biochemistry is extremely intricate. Phosphates are required for all life, but are typically limited in reef and marine aquariums to avoid algae growth. Planted aquariums require phosphorous, and its exclusion has become popular. However, phosphate buffers are frequently employed in growing aquatic plants on a large scale. Tap water usually requires enough phosphate for the planted aquarium, or you can dose with different salts depending on your tank’s pH. Chemical media, downforce protein skimmers, and biological filters remove phosphate.
Silicates are a favorite of diatoms. In either freshwater or saltwater, elevated silicates results in algae. Diatoms can extract silica from glass. Chemical media and downforce skimmers remove silica. Often, the same media removes phosphates
Chloride is extremely important to freshwater plants. Chloride is readily available in most water sources. Do not confuse with chloramine, which is also available in most water sources but is dangerous.
In general try to avoid taking material out of the aquarium. An excellent example would be to run foam fractionation (skimmer) on a sump, send the top fraction to a phytoplankton culture, have the phytoplankton overflow into a refugium, have the refugium empty into the display tank, which overflows into the sump. Each separate container would have its own lighting, substrate, and circulation. In this way, you really never have to add anything to the tank except water. The only cost is power, water, and lamps. Additives can be homemade by removing excess algae and aragonite and grinding them in a mortar and pestle.
Another example is a planted aquarium. A single display tank, a quality canister filter, a reverse flow under gravel filter, and fluorite ore substrate takes care of itself. Just replace evaporated water with water rich in potassium and phosphates, over feed the fish, and replace the lamps and filter floss twice a year. Plants take care of the rest.
Also, avoid adding extra heat to the aquarium. Use external pumps instead of powerheads. Acrylic aquariums can easily be machined to accept standard plumbing fittings. Make sure your plumbing has long radius turns and clean walls. Cooling your lights helps prolong lamp life and lowers water temperature. Place your heater inline with circulation plumbing. Make sure the entire tank is circulated. Dead spots make scary chemistry.
Many of the products available are marketed very, very well but provide little advantage if any to a less expensive alternative. So keep your wits about you and do your homework. In the end, your pets will be happier, your aquarium will look better, and you will spend less money.