Saltwater Aquarium 101

HOW HARD IS IT TO KEEP A SALTWATER TANK? We hear this question daily, from just about everyone who walks through our door and sees how beautiful a properly set up marine tank can be.  The answer is simple:  with the right combination of basic knowledge and quality equipment, anyone can have a successful saltwater aquarium.  From a beginner's basic tank with just a few clownfish to the most advanced high-end custom reef aquarium with dozens of live corals, all successful marine aquariums share many of the same principles.

A few common mistakes to avoid when starting a marine aquarium:
1.     Failure to plan ahead
2.     Failure to read current, reputable marine aquarium books, or otherwise research the hobby to gain a basic knowledge of equipment and methods prior to making the big purchase
3.     Relying on unqualified individuals or sources for advice.
4.     Starting with an aquarium that's too small
5.     adding fish and corals too quickly
6.     using unfiltered tap water
7.     using outdated, ineffective or inadequate equipment
8.     using the wrong substrate
9.     positioning the aquarium near a window, heater, or drafty area.
10.     not testing the water
11.     purchasing unhealthy or poorly conditioned animals
12.     purchasing fish on impulse, rather than planning ahead
13.     purchasing fish that are incompatible or that grow too large for your aquarium
14.     adding newly acquired fish to an established tank without quarantining them first.
15.     adding harsh fish medications to an aquarium containing invertebrates
16.     Not cleaning out the protein skimmer frequently
17.     Adding uncured live rock to an established aquarium
18.     Purchasing photosynthetic animals such as corals and tridacna clams without first installing adequate lighting to sustain them.

  We will now briefly discuss some of the basics of a marine aquarium.


1.)     Biological Filtration:  Biological filtration refers to the purification of aquarium water by beneficial aerobic bacteria colonies.    The input of fish food and fish waste into the closed-system aquarium produces toxic ammonia and nitrite.  These compounds need to be broken down and removed from the aquarium if invertebrates and fish are to thrive in the tank. Both of these compounds are toxic to most organisms and are removed from the aquarium by beneficial bacteria colonies living in the filter, or within the live rock and live sand (if present).  The oxygen-consuming bacteria utilize oxygen to convert toxic ammonia and nitrite into nitrate, a much less toxic byproduct.  During the first several weeks that a new marine aquarium is established, ammonia and nitrite will be present until sufficient bacteria colonies have developed in the filter system to reduce their concentrations.  Test kits are used to monitor water quality during this crucial time.  Damselfish, hermit crabs, tank-raised clown fish, cured live rock and live sand are often placed into the aquarium first, until the bacteria colonies are fully established and water quality becomes optimal.  Once the ammonia and nitrite levels have dropped to zero, the tank is considered cycled. (usually 6-8 weeks).   Nitrate, the final byproduct, will accumulate in established aquariums, but is nontoxic to fish in low concentrations (up to 20 ppm).   Nitrate can, however, cause the development of unwanted nuisance algae, so it is important to keep the level as low as possible.   Nitrates can be kept under control by performing regular partial water changes with nitrate-free water.  Live sand beds of at least 4 in depth have been found to reduce nitrate buildup as well, through the use of an anaerobic bacteria colonies which use nitrate as a food source within the live sand bed.

2.)     Salinity:  Salinity is the measurement of the total dissolved salts in the aquarium, and is usually expressed in Parts Per Thousand (ppt). Specific Gravity is the measurement of the density of water, and is expressed as a decimal.  Pure freshwater has a Specific Gravity of 1.0.  Saltwater aquariums are usually maintained at a S.G. of 1.020-1.026, depending on the type of organisms maintained in the aquarium.  Reef aquariums or any aquarium housing invertebrates generally needs a higher S.G., while aquariums housing only marine fish are best maintained at a slightly lower S.G.   The devices used to measure S.G. are either a hydrometer or a refractometer, and is an absolute necessity for all marine aquarium owners.  Most devices display specific gravity as well as salinity, and are usually calibrated for use with marine aquarium temperature water.


SeaWater Hydrometer, by Red Sea

3.)     Ph Level:  pH level is the measurement of the hydrogen-ion concentration of the water.  A pH of 7.0 is neutral, a pH of less than 7 is acidic, and a pH of over 7 is alkaline.  The ideal pH for a marine aquarium is 8.1-8.4.  Excess fish food and waste, biological filtration, tap water, the decay of algae, bacteria and other organic compounds all contribute to the decline of pH levels in the marine aquarium.  The aquarist must monitor and adjust the pH of their aquarium to maintain the correct levels.  Since extreme fluctuations cause stress to the fish and invertebrates, the exact pH level maintained is less important than the stability of the pH.  Aqua Dreams uses and recommends several buffers and test kits to build and maintain the pH level in the marine aquarium.  It is highly recommended to add pH buffer into the top-off (fresh) water that is added to replace water lost to evaporation.  This procedure will help eliminate pH swings due to adding large volumes of tap-water (with a relatively lower pH) into a high-pH marine aquarium.

4.)     Temperature:  The ideal temperature for a marine tropical fish aquarium is 78-82 degrees Fahrenheit.  The ideal temperature for a reef aquarium is 75-78 degrees Fahrenheit.  Maintaining a stable temperature is of the utmost importance, since the incorrect temperature or temperature fluctuations can cause stress to the inhabitants of the aquarium, and can lead to disease and algae outbreaks.  We recommend using a high-quality submersible heater with approximately 3-4 watts per gallon of tank capacity.  In addition, use only water with the correct temperature for all water changes and top-offs, especially during winter months when tap water can run extremely cold.  Even just a few gallons of top-off water that is the incorrect temperature can cause the temperature in the aquarium to drop.  Be sure to purchase a reliable thermometer and secure adequate circulation to assure a uniform temperature.  


1.     TANK- Ok, this one's obvious!  Choose a tank that is low and long for best success.   Extremely deep, narrow, or odd shaped tanks such as hexagons, are not ideal saltwater aquariums.   Choose a tank with the largest surface area possible.  Remember, the tank itself is one of the smaller expenses of a marine aquarium, so don't sell yourself short.  The larger the tank, the more stable the environment that can be created.  Small marine aquariums require a lot of attention and put greater limits on the selection of fish and invertebrates that may be maintained.   Shorter aquariums allow a greater intensity of light to penetrate the water for the animals that require it, where tall tanks create much more of a lighting challenge and expense.  Also consider some of the All-in-one styles, such as Biocube & Red Sea Max- both offer the hobbyist a simple boxed tank set with most of the components included for one price, often saving the hobbyist money at start-up. 


2.     COVER,  LIGHT-  Glass Covers are available in all sizes and will help keep fish from jumping.  Next the hobbyist should consider lighting.  Prior to choosing a lighting system for your aquarium, you must ask yourself a few questions.  Are you planning a fish-only tank, or a tank that will house live rock, coral, anemones and other invertebrates?  If you are planning on keeping mainly fish, and/or non-photosynthetic invertebrates (starfish, urchins, crabs, snails, etc.) an inexpensive fluorescent-type aquarium light should suffice.  We use and recommend T5, high-output fluorescent lighting, T5 refers to the diameter of the bulb, which is very thin, powerful, and bright.  Although it is possible to change the color spectrum of a standard fluorescent lamp, changing or increasing the intensity of the lamp with a standard fixture is not possible- so consider T5 High Output fixtures.  Only choose a standard fluorescent light if you dont plan to keep photosynthetic animals.  If you plan to keep a reef-type aquarium which houses photosynthetic animals such as corals, a lighting system with greater intensity (power compact, T5'S, metal halide, LED's) must be purchased that can achieve the intensity needed for these animals to thrive.  Aqua Dreams can help the consumer choose the correct lighting system for your aquarium type. ( Beware of the common beginners mistake:  Do NOT purchase sea anemones, corals, tridacna clams, etc, unless you have the lighting intensity to support them.  These animals obtain most of their nourishment through photosynthesis occurring within a symbiotic algae living in the coral tissue,  and will perish in your aquarium without the proper lighting intensity.) 
3.     CABINET, OR STAND- Choose a sturdy wooden or metal stand capable of supporting the weight of a filled aquarium.  Even a 20 gallon tank can weigh 300 lbs once it is full of water, sand, and rock, so plan accordingly.  Do not place a filled aquarium on an entertainment center or near any television or other electrical equipment.

4.     FILTER-  What type of filtration should you choose?  To achieve biological filtration, surface area for bacteria colonization is of paramount importance.  If the beneficial colonies of bacteria have nowhere to grow, water quality problems will occur.  Biological filtration will occur on the bio-wheels, filter cartridges, bio-balls, and other surfaces within your filter.  Be sure not to kill all the good bacteria by over-cleaning your filter.   Chemical filtration, which reduces impurities and organic build-up, is accomplished through the use of activated carbon.  Carbon filtration will reduce discoloration and odors in the aquarium water.  Old carbon no longer absorbs impurities, so changing the carbon filter regularly is recommended.  Choose a larger filter than you think you will need.  Larger filters will reduce maintenance and provide a cleaner aquarium for a longer period of time before requiring service.  The filter system is like the engine in your car, so care should be taken when selecting the filtration for your aquarium.

5.     HEATER  & Thermometer -  Most aquarium heaters on the market today are very reliable.  We highly recommend the submersible type, which allows the hobbyist to dial in the correct temperature and submerse the heater completely underwater.  Most heaters are made of glass, and are very breakable.  Always unplug the heater before servicing the tank, and plug it in only after completing the service.  Use a reliable thermometer to monitor the temperature and make any adjustments as necessary.  Do not make the mistake of unplugging the heater in hot weather, if the aquarium temperature is higher than the heater setting, the heater will not operate.  When the tank begins to cool back down below the desired temperature, the heater will  come back on to maintain the desired temperature.  In very hot climates, a refrigeration device, called a chiller, may be necessary to reduce and control heat buildup

6.     PROTEIN SKIMMER - Protein skimming can be defined as the separation and removal of dissolved organic toxins from aquarium water.  Biological filtration can only reduce ammonia and nitrite levels, but it cannot reduce or remove dissolved proteins and organic waste resulting from feeding, fish waste, nitrification and other metabolic processes occurring within the aquarium.   A properly functioning protein skimmer will reduce dissolved proteins, toxins, and organic waste, all of which are toxic and dangerous to the fish, corals, and invertebrates living in our aquariums.  Protein skimmers use a process called foam fractionation to separate the dissolved waste from the water, and deposit it in a collection cup for easy removal from the system.  Protein skimmers can be installed on the back of a tank, or beneath the tank in a wet-dry filter system or sump, depending on the configuration of your system.  Aquariums housing invertebrates, corals, and live rock are most dependent on protein skimming for the majority of the water purification.  Be sure the skimmer is correctly sized and operating efficiently at all times.  A poorly maintained skimmer will not perform as well as a skimmer that is cleaned and maintained regularly.  Be sure the column is full of white air bubbles and the collection cup neck is clean, so the organic waste can rise up the neck into the collection cup.  Common skimmer malfunctions include: pump failure caused by debris and algae blocking intake screens, reduced air flow caused by blocked or clogged venturi valves or air intake tubing, and a reduction in organics collection due to sludge build-up within the reaction area.  Protein skimmers may be used in conjunction with bio filters in saltwater fish aquariums, or used alone in a reef aquarium as the sole type of filtration.
7.     HYDROMETER, REFRACTOMETER-  A device that measures salinity or specific gravity.  Cannot operate a marine aquarium without a reliable hydrometer.  Useful for measuring the amount of salt dissolved in the aquarium, and also for mixing new saltwater prior to adding or changing the water in the tank.  Hydrometers are lower cost and slightly less accurate.  Refractometers are slightly more expensive but deliver more accurate readings.  They can be calibrated for efficiency, and do not generally wear out like hydrometers can.


8.     TEST KITS-  Since we cant determine water quality parameters by sight, we must rely on test kits to monitor and control the environment within our marine aquarium.  Most common test kits include, but are not limited to:  pH, Ammonia, Nitrite, Nitrate, Alkalinity, Calcium, and Phosphate.  Ammonia and Nitrite kits are critical during the first several weeks to monitor the development of biological filtration within the aquarium. pH kits are used regularly to determine pH fluctuations which may need to be corrected.  High nitrate and Phosphate levels can lead to undesirable algae blooms, so we are interested in testing and keeping these levels as low as possible.  Alkalinity refers to the total dissolved carbonates of our water, and has an impact on the stabilization of pH levels.  Calcium test kits are used to monitor Calcium levels in reef aquariums, where optimal calcium levels are required for the success of our corals.  Be sure to select the correct test kits for your needs.  Aqua Dreams stocks a wide variety of useful test kits, and we can help you in selecting and using the test kits that are right for your situation.

9.     SUBSTRATE -  This refers to the material on the bottom of the marine aquarium, usually comprised of calcium and magnesium carbonates.  The collective term for material comprised of the correct minerals for marine aquarims is aragonite.   The aragonite substrate will assist in maintaining alkalinity and pH levels in marine aquariums, as well as create a breeding ground for beneficial micro-organisms that will assist in the breakdown and processing of wastes in the aquarium.  Live sand is the collective term used for marine aquarium sands that are containing live bacteria and micro-organisms.  Live sand beds of 4 or greater will enhance nitrate reduction in the aquarium, harboring anaerobic bacteria in the low-oxygen layers of sand.  These bacteria live without oxygen, and will consume nitrate as a food source, further purifying the water in a reef aquarium.  Generally live sand is used in reef aquarium, normal aragonite or crushed coral is fine for fish aquariums.  The substrate in a fish aquarium can be vacuumed out regularly during the monthly partial water change to remove debris from the bottom of the aquarium.   If necessary, we recommend vacuuming only the top quarter inch of sand in a reef aquarium with live sand, never vacuum below the top surface of the live sand bed, which would disrupt the processes occurring therein.  We can assist you in determining total volume of substrate required, grain size and total sand bed depth, prior to purchasing the substrate.
10.     MARINE SALT - Ocean salt mixes can be purchased in anywhere from 5 gallon mixes to 200 gallon mixes.  When mixed with pure fresh water, the marine salt mixes will produce pure almost-natural seawater, safe for all marine life.  Be sure to completely dissolve the salt mix in the correct temperature water.  Aeration and circulation of the newly mixed seawater will assist in the proper gas exchanges and ensure that all of the salt is completely dissolved.  Note: always use a hydrometer when mixing saltwater.  If the level is too high, add freshwater.  If the level is too low, add salt.  Always dissolve salt in 75-80 degree water in a separate bucket or other clean mixing receptacle.  Never add or dissolve salt inside an aquarium containing fish or invertebrates.  Do not add water to aquarium until salts are completely dissolved, water is aerated, and the correct temperature and specific gravity are achieved. 

11.     TAPWATER PURIFICATION - To reduce algae problems in marine aquariums, many hobbyists are employing some type of tap-water purification, prior to using the water in their aquariums.  Tap-water routinely contains contaminants and impurities that will affect the conditions inside our marine aquariums.  Some of the impurities include copper and iron, usually from metal pipes and wells, bacteria, phosphate and nitrate (algae- promoting nutrients), chlorine, chloramines, ammonia, and silicates.   These compounds may not affect our health or the taste of drinking water in small amounts, however they can create unfavorable conditions for invertebrates and fish living in our marine aquariums.  Many of these compounds promote nuisance algae such as hair algae and cyanobacteria (slime algae) that can overgrow a reef tank and ruin its appearance.  Reverse osmosis units and deionizers are the most common methods for purifying tap-water.  Miniature drinking water filters attached to faucets do not provide the degree of toxin removal and purification required to improve the conditions of tapwater for aquarium use.

12.     WATER CIRCULATION - One of the most overlooked aspects of marine aquariums is water movement.  Circulation of the water carries waste away from benthic invertebrates and corals.  Circulation will bring foods such as phytoplankton to the live rock and corals.  Circulation will help carry contaminants and detritus to the protein skimmer and biofilter.  Circulation will aid in the proper gas exchange between the water column and the air above it.  Circulation will spread oxygen-rich water throughout the tank to the fish and invertebrates that require it to live.  Circulation will help eliminate dead spots where contaminants could settle, causing localized algae blooms.   The proper amount of water circulation may require some advance planning and forethought, prior to installing the system.  Submersible pumps are the most common way to achieve the correct amount of water flow in the aquarium.

13. REFUGIUM-      A refugium is quite simply, a sheltered area from the main aquarium.  Usually hanging on the tank or sump, refugiums hold a small amount of live sand or  refugium mud on which plants are placed.  A light is placed over the refugium, and tank water is pumped through it very slowly.  Refuiums can be used to achieve three objectives in a reef-type aquarium.  The first and most common reason for adding a refugium is nutrient export.  By growing marine plants, called macroalgae within a refugium, the algae-promoting nutrients such as nitrate and phosphate are reduced or eliminated from the aquarium water.  The plants in the refugium soak up these nutrients, leaving little or no nurtrients for undesirable slimy or hair algae to take over in the main tank.  By trimming and removing a portion of the plants from the refugium regularly, new growth is encouraged and nutrients are removed from the system.  The second reason for adding a refugium is to produce a source of live food for the aquarium's inhabitants.  Tiny marine crustaceans will congregate in the algae of a refugium, slowly filtering out into the main tank providing a source of nourishment for fish, corals, and anemones.  Lastly, by lighting the refugium at night when the main tank's lights are off, pH swings are avoided when the photosynthesis in the main aquarium stops at nightfall.   A refugium works in conjunction with a protein skimmer to reduce the excess nutrients that cause undesirable algae in our aquariums.