R  e  e  f    A  q  u  a  r  i  a

An aquarium type that provides a challenge for even the most advanced aquarist is the reef aquarium.  However, the rewards offer one of the most breathtaking pieces of aquatic decor available in the aquarium hobby.  The reef aquarium is loaded with life from fish, and coral, to rock and sand.  There are often many types of creatures in this type of aquarium that give a reef many things to observe.  This aquarium type provides a dramatically evolving environment for the life of the tank, and a centerpiece for anyone's home or office.

This section is dedicated to the coral reef aquarium, and the aquarist who cares for them.  Due to the complexity of this end of the aquarium keeping hobby, this section could be, and is the subject of volumes of books, magazines, and websites.  However, we will cover the basics and fundamentals of the reef aquarium, the different types of reef aquaria, and what is the best way to maintain one.


Principle and Method

There are many opinions and techniques about taking care of reef aquariums available today.  However, all of these techniques work toward the goal of sustaining the immense amount of life commonly kept in the marine mini-reef.  This can be a trying chore if the proper environment is not properly established and maintained.  It's usually a good idea to have a particular setup planned out in detail for this type of investment, and it's definitely not recommended for the beginning aquarist.

The most important factors of taking care of a reef aquarium are: water quality, filtration, lighting,, environment control, nutrition, and maintenance.  These factors are important in almost all aquaria throughout the hobby, but the requirements of the marine reef aquarium are such that amplify these factors, and precision is required for success.

The challenge of the reef aquarium can be complex in many ways, and the maintenance schedule for certain setups is daily, but others are more self-sustaining, and require little maintenance, if any.  The main types of systems we consider are the Jaubert method, the Berlin method, and a hybrid of the two, newly known as the North American method.  These methods will briefly be discussed.

The Jaubert Method (also called plenum method) is one in which thick beds of substrate (crushed argonite, shells, coral, or live sand) and large amounts of live rock allow the aquarium ecosystem to "naturally" break down wastes, and maintain high water quality.  A "plenum" is established by using live sand as a natural denitrifing bed.  A good thick layer is often mandadory for achieving this effect.  Chemoautotrophic bacterial growth will occur in the absense of oygen, so a thick layer (2"-4") is often necessary in separating the high oxygen environment of the reef to the completely anaerobic environment for bacterial growth of the plenum.  These anaerobic bacteria consume nitrate, allowing the biological filter to naturally cycle. This is probably the most trouble-free system, if set up correctly.  Care needs to be taken in the proper maintenance of the rock and sand by adding organisms such as shrimp, cucumbers, snails and other maintenance type creatures to naturally care for the ecosystem.

Live rock contains billions of nitrifying bacteria that consume ammonia, and nitrite, among other components, and thrive in the presence of stable, oxygen-rich water.   Concentration is also on maintenance type creatures to assist in the Jaubert Aquarium's success.  Some of these would include various shrimp, nudibranchs, snails, crabs, hermit crabs, stars, sponges, filter feeding organisms, or cucumbers.  A common filtration device for this type of system are circulation pumps, cannister filters, algae turf filters, trickle systems, power filters, and many other various designs.  Careful consideration needs to be given in this area as many marine organisms may not be compatible, or may destroy the reef.

The Berlin Method focuses more on the filtration components, rather than the organisms themselves to simulate the natural environment in the aquarium.  Especially in the last decade, Berlin aquarists have many options in many types of high-tech equipment available to them.  Heavy emphasis is put on auxiliary filtration (protein skimming, ultraviolet sterilization, ozone, reactors, advanced filtration) in particular though on the use of efficient protein skimming to remove toxins from the aquarium water.  Most filtration units for this type of system have a large amount of "bio media", which are usually plastic/ceramic spheres or disks.  These are used to grow large amounts of nitrifying bacteria when oxygenated water is constantly run over and through them.  Many Berlin systems also incorporate different mechanical and chemical filtration options, as well as different monitoring and controlling equipment.  This type of system can offer a real challange to the expert aquarist.

The North American Method is the newest method, and is basically a combination of the two above methods.  On one end, you have access to advanced filtration, and monitoring devices, and on the other you have the live rock, plenum, and maintenance creatures to allow the natural effect for the mini reef ecosystem.  This method is often the most costly, and can take an aquarist years to build just one aquarium system.  Careful planning is required for all of these methods, but especially with regard to this method because of the overall complexity and cost of the system.  This type of aquarium is often found loaded with life, and a healthy dose of daily maintenance is required both for the equipment and livestock.



Since the water is the environment of the aquarium's inhabitants (as air is to us), it is obviously a very important factor in maintaining a successful reef.  A true reef aquarist needs to become familiar with looking at the water through a chemist's eyes, and understanding the different types of reef environments in nature.  Testing and monitoring water elements on a regular basis should be a regular task in maintaining these aquariums.  It is vital to use water in the reef that has things such as: proper temperature, pH, salinity, alkalinity, redox potential,  dissolved oxygen, carbonate hardness, trace elements, and trace elements.   These will briefly be discussed.

Temperature-There are arguments as to where the mean temperature of the reef should be.  A common thread of agreement though, is that the temperature remain constant.  We keep our reef aquaria in the 76-78 F range, and only allow a maximum temperature change of 2 F in a 24 hour period.  Many people not only use heating on this type of tank, but also chilling systems.    Some professional aquarists contest that coral growth is much better in the 80 F range, however water quality needs to be absolutely impeccable.  Temperature control make a huge difference on the vitality of animals, especially tropical reef specimens where temperature fluctuations in the wild are minimal.

pH-The pH of the reef aquarium should be kept as stable as possible.  However, the pH will normally fluctuate up to a full point during the course of one day.  This is the result of metabolism, photosynthesis,  nitrification, excretion, and other various long words.  PH is often controlled with the maintenance of the calcium and alkalinity levels.  Most tropical mini reefs are kept in the pH range of 8.1 to 8.5 with 8.3 being the recommended mean pH reading.

Salinity-The salinity of natural seawater is around 1.025.  In the marine aquarium, and including the reef, we recommend to keep the salinity somewhat lower.  1.019 to 1.023 is where we keep most of ours.  This is especially helpful to the fish with regard to toxic shock, and disease control.  It slows metabolic rate in many different types of species, which some contest allows the aquarist an advantage for long term success.  It's important to understand that stability is important with regard to salinity, too.  Many trickle type filters require high water movement and have open sump areas where water is exposed to air.  This allows for rapid evaporation, causing the salinity to rise dramatically in just a few days.  Care needs to be given in the area of water replacement.  This may have to be done every few days to maintain constant salinity.  Many corals are especially sensitive to salinity changes and can become infected by a variety of diseases, or even die of toxic shock.

Alkalinity-The alkalinity affects, and is affected by the buffering system of the marine system.  A high alkalinity reading often gives way to a more stable pH measure.  Total alkalinity measure the amount of acid (positively charged) that is required to neutralize all the negatively charged carbonate, bicarbonate, and borate ions present in one liter of water.  Natural seawater is about 2.1 to 2.5 meq/l, which is about where the mini reef should be kept.   One meq/l is equal to about 50 ppm calcium carbonate.  There are many good alkalinity buffers now available to help keep this important measure in check.

Redox Potential-Measures the oxidation-reduction potential of the water molecules in the system.  This was originally a European measurement of water livibility, but is now used worldwide, especially in the reefkeeping trade.  The is measured in millivolts (mV) and most successful reef aquariums are kept in the 350-400 mV range, although some are kept even higher.   A high redox potential usually indicates proper nitrification from the filtration, and excellent aeration.  Some reef aquarists swear by using ozone (usually in reactors or protein skimmers) to control this measure.  Ultraviolet sterilizers are also used for this measure.  A good air pump, and regular aquarium maintenance are also easy ways to keep this reading high.

Dissolved Oxygen (DO)-Too many novice aquarists under-estimate the power of oxygen in the aquarium environment, especially in the reef.  Total dissolved oxygen measures the available amount of oxygen that is available in it's dissolved liquid state within the aquarium water.  The idea is to saturate the water with oxygen to stimulate the growth of a number of different organisms.   Natural reef areas usually have very high oxygen levels due to the churning of the water and changing of the tides.  Water movement is also very important in the reef aquarium and will aid to increased DO levels.  Powerheads and water pumps will help to achieve this effect.  

Oxygen reactors have also become popular over the past few years.  These are columnar pressurized devices that run water over some type of  bio media.  The increased pressure, along with the addition of air allows the oxygen to saturate the water with just a point or two increase in psi.  This device is often run with both an air and water pump and will maintain very high DO levels.

Carbonate Hardness-This is a very important test in the reef aquarium because of the amount of life that consumes major elements such as calcium from the water.  This test is basically a measure of the amount of available calcium carbonate in the reef water.  Biological filtration and the breakdown of organic wastes will also aid to the decrease of this reading.  Many systems have to constantly replace trace elements, and calcium to keep the water "hard" in calcium levels.  More advanced systems have calcium reactors, CO2 systems, dosers, and dosing pumps for the controlled addition of calcium to the reef.

Trace Elements-Not only is calcium utililized by the fish, corals, rock, sponges, and other life in the tank, but many other trace elements are, as well.  Careful monitoring of the amount added per given time should absolutely be adhered to.  Increased levels of chemicals such as Iodide will kill life quicker than about any disease.  Use quality name products and dose exactly to the recommendations of the manufacturer.  Use quality test kits when testing chemical levels.  More advanced aquarists will monitor these levels on a regular basis.  Water changes are sometimes necessary to adjust levels, just as increasing dosage would do the same.

Filtration, especially protein skimming also needs to be taken into consideration when adding trace elements.  This device, if efficient, has the ability to remove these trace elements in short periods of time.  Care needs to be taken in properly maintaining the protein skimmer's functionality.  Many other auxiliary filtration devices will also dramatically effect these levels in the reef aquarium.  Sometimes it's good to shut off devices like protein skimmers, uv sterilizers, ozonizers, etc. for short periods of time immediately after adding elements to allow the reef water to have more time to "absorb" these elements.  Common trace elements added are strontium, molybdenum, iodine, iodide, borate, magnesium, calcium, and many others.



Proper filtration is crucial in maintaining a reef aquarium.  The main elements of aquarium filtration are biological, mechanical, chemical, and auxiliary.  We will briefly discuss each of these in relation to the reef aquarium, but for more general information you can consult our Aquarium Filtration section.

Biological Filtration-I am an advocate of the natural reef (Jaubert, or North American system).  Traditional biological aquarium filtration for the reef aquarium cultures both autotrophic and chemoautotrophic bacteria in devices such as bio chambers, bio towers, trickle filters, overflow boxes, denitrifiers, and algae turf filters.  However the natural or Jaubert system (see above) utilizes live sand, live rock, and the organisms themselves, and for maintaining huge colonies of bacteria.  The idea is to grow billions of nitrifying bacteria, and other bacteria to aid in the natural breakdown of fish waste, toxic chemicals, and organic matter.  This can be achieved by many different methods described above.  High oxygen content, stable temperature, and good water flow are the main products of success to develop the aerobic filter.  Low oxygen content, and water flow is beneficial for the anaerobic filter.

Mechanical Filtration-The idea here, is to physically remove detritus and waste products from the aquarium water.  This can be achieved in many different ways in the reef aquarium as there are many designs of filters to accomplish this effect.   Oftentimes this is done by trapping the particles in media such as different cloth pads (such as cotton or Dacron), overflows, bio chambers, pleated filters, and any other area that is exposed to constant water flow where debris can be trapped.  Mechanical filters can get very dirty in certain reef applications because so much waste is being produced.  Another reason to keep them maintained is that they trap debris and hold high levels of nitrate, and other toxic chemicals.  Thus, mechanical filters need to be cleaned and/or replaced on a frequent basis.

Chemical Filtration-This is the process of chemically purifying the water through means of sterilization, chemical adsorption, electron ion exchange, or molecular breakdown.  Chemical filtration can be very effective, but can also degrade the aquarium water if not maintained.  For example, charcoal of poor quality, or that's never changed will tend to leach phosphates, silicates, or other pollutants into the aquarium water that will lower water quality, and harbor the growth of undesirable algae in the reef.  Make sure to use high quality carbon, and realize it's only for temporary use and either needs to be replaced, or removed regularly.  Porous, or "acid washed" carbon if very effective in reef applications.  Charcoal is also effective for removing medications, and trace elements from the water.  Limited use is recommended.  

Poly adsorption pads and disks are also effective chemical filtrants available.  These are very effective in targeting certain chemical components (ie, phosphate, nitrate, copper) that are harmful to the reef.  These have limited time use as well, and should be replaced at the recommendation of the manufacturer.  Protein skimming could also be considered chemical filtration by the action of oxygen in the skimmer's chamber, and the way it removes chemicals from the water.

Auxiliary Filtration-This is all of the other equipment that is available to the aquarist that are none of the above.  Many auxiliary devices are available to help improve different aspects of the water quality.  It seems new auxiliary devices are popping up every day.  These devices include uv sterilizers, reactors, skimmers, co2, algae turf filters, controllers, probes, and other monitoring equipment.  Make sure your reef will benefit from the use of these products, and choose this equipment with extreme care.  There are many "toys" or low-end products in this area, and one can make expensive mistakes if not chosen carefully.



Lighting is yet another crucial element in maintaining a successful reef aquarium.  Proper amounts of light are especially important in the reef because often many of the organisms need the intense light as a food source, and others indirectly need it simply for the simulated sunlight effect that is very intense over most tropical reef areas.  For a more detailed look into the the different types of lights available to the aquarist, please see the Aquarium Lighting section of this site.

It is wise not only to choose the proper wattage for the bulbs, but lights of the proper spectrum as well.  The degree Kelvin (K) reading gives a measure of this.  The higher the degree K, the bluer the light becomes.  In other words a 5000K bulb is more yellowish in color.  A 10,000K bulb is of an ice blue whitish tint.  The 20,000K bulb is a very blue tinted bulb.  It's also important to look at the Color Rendition Index (CRI) rating for the bulbs used.  This is a good measure of overall bulb intensity.  A CRI rating in the 90's is desirable for most reef aquaria.

With every inch of aquarium space you go deeper into the reef tank, you significantly cut down on the amount of light intensity.  For a rough estimate, we recommend 5 to as much as 10 watts of lighting per gallon of aquarium for the reef.  If the aquarium is a tall or deep in design, special considerations need to be made for lighting.  We recommend a longer, more shallow aquarium for a reef tank, as opposed to a shorter, taller tank.

Fluorescent lights-are energy efficient and offer good supplemental lighting for most reefs.  Many aquarists who put emphasis on blue lighting use fluorescents for this purpose.  Others use many strips and use High output (HO) or Very High Output (VHO) bulbs as the sole lighting source.  This type of design can be space consuming, and more maintenance intensive, but are often very effective, and offer the reef aquarist on a budget an advantage.

Compact fluorescent lighting-are basically very bright, and smaller fluorescent bulbs than their relative HO, or VHO fluorescent bulbs.  This special type of fluorescent lighting has unique phosphors that illuminate intensely when electrified.  These bulbs have average to long bulb life (12 to 16 months), and are extremely efficient.  They have quickly become very popular in the reef hobby, and many outlets carry the hoods and replacement bulbs.  The bulbs do not get too hot, and are often sleek in design, making them very versatile to mount.  Some aquarists mix them with other lighting forms (i.e. metal halide, fluorescent, incandescent) to get a unique effect.

Metal Halide Lighting-This lighting type is excellent at producing large amounts of light, and the bulbs are now available in many different spectra, wattages, and CRIs.  These are often mounted as hoods, or pendant lamps.  There are also many high tech designs available to the perfectionist.  This unique lighting offers the unique luminescent "dancing water" effect that is created from the light and water.  Metal halides have been used with much success for many years, however care needs to be taken not to burn the corals.  Ultraviolet shields, and covers are readily available.  It's wise not to expose the bulbs directly to the tank.  Some corals are very sensitive to ultraviolet burn, and can be killed as a result of this condition.

Care needs to be taken to replace the bulbs at the recommendations of the manufacturers.  The bulbs are usually rated by hours, so you may have to calculate how many hours a day, week, month, year your bulbs are being used.  Even the slightest shift in light spectrum, or dimming can cause stunted growth, or even disease infection.  Regular maintenance of bulbs is required, and should be done with regularity.  Account for bulb expense when the aquarium is initially planned, as some reefs lighting requirements can be costly.



Importance of nutrition, again, is amplified in the reef aquarium due to the diversity, and amount of life present.  Daily care should be given in the feeding regimen.  It's better to feed smaller amounts of food more often, than large amounts at one time.  Many reef aquaria have both coral, inverts, and fish, so consideration needs to be given to all three.  In some systems it's smart to turn off water pumps and powerheads to keep the food from getting clogged into overflows, pumps, and filters.

Coral-Many corals feed many different ways.  Some of these ways include: photosynthesis, filter feeding, carnivorous, and stinging.  It's important to understand the biology of the specimens you are keeping, which, unfortunately, is beyond the scope of this page.  It will then be possible to determine how much, what type, and how often food should be administered.  Many coral foods are in liquid or powder form.  Live microorganisms such as daphnia, brine shrimp, rotifers, and phytoplankton are always good food choices for a reef.  Calcium is also considered a food source, as is lighting.  Certain foods are also constantly dosed to the aquarium water with dosing devices.

Invertebrates-Many of the critters roaming throughout the reef (that aren't the fish) are the invertebrates.  Some of these are critters like shrimp, lobster, nudibranchs, worms, crabs, hermit crabs, sea apples, cucumbers, and others.  These eat a variety of foods, decaying matter, and sometimes each other if unwatched!  Live food is always a good option such as brine shrimp, daphnia, krill, rotifers, and water fleas.  There are also good freeze dried, and sinking pellets for crabs, shrimps, and anemones.

Fish-The nice thing about feeding reef fish is that they are motile, and usually will eat a variety of foods.  There is also a huge variety available for tropical fish including freeze dried, live, and frozen.  Use only the highest quality food products you can find for your reef.  This practice will return the favor, if done correctly, and your fish will thrive.  Feed your fish a up to a few times a day.  Learn the likes and dislikes of each specimen in the aquarium.  Proper diet is key to success, and can be a challenge with species of fish such as angels, butterflies, gobies, and various other reef fish families.  

Concluding, as you can see, the reef hobby is one that can be complex and intimidating to some at first.  However it can also be a very rewarding end of the aquarium keeping hobby, and hopefully it is a science that will help to one day restore our ocean's reefs by the study of their environments.  Other areas of this website have information about keeping aquariums that is also beneficial to the reef enthusiast.  Good luck, and happy reefkeeping :)


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