Water Quality and Aquarium Maintenance

Improper water quality and inadequate aquarium maintenance are the primary causes of fish disease and fish death. The purpose of this handout is to briefly discuss the various water quality parameters, which need to be understood and monitored to ensure a healthy aquarium environment. We then will discuss aquarium maintenance as this directly impacts your overall water quality.

Water Quality Parameters: 

  • “Tap water is supplied for one purpose – human consumption. It is carefully screened, cleaned, treated with prophylactic chemicals and pumped into our homes for our use. It does not, however, carry a guarantee that that it is suitable for fishkeeping!” (The Encyclopedia of Tropical Aquarium Fish; Dick Mills and Dr. Gwynne Vevers; Tetra Press; page 24). Reverse osmosis (RO) water is “tap water” that has been processed to strip 99% of all contaminants out of the “tap water.” This pure water is absolutely the best water to use for all types of aquariums. Reference is made to “How to Control Algae” handout. 
  • It is imperative that the hobbyists have an understanding of the properties of water, the importance of maintaining water quality and the necessity of using test kits to monitor water quality. 
  • In all instances it should be noted that the appropriate water temperature is as critical a factor to the success of your aquarium as any other parameter. Understand your specific temperature needs and maintain them accordingly. 
  • The following water qualities can, and should, be tested with the appropriate aquarium test kits on a regular, continuing basis or whenever something appears to be amiss.


pH of water is a measure of acidity or alkalinity. The pH ranges from 0 to 14, with 7 as the neutral point. Above pH 7 water is alkaline; below 7 it is acidic. Charlotte tap water will USUALLY measure between 8.0 and 9.5. This is NOT ACCEPTABLE for MOST freshwater species you will encounter. Goldfish, Gouramis, Livebearers, South and Central American Cichlids, Tetras, Rainbows, Danios, etc. require different water parameters. ALWAYS test tap water pH prior to making freshwater aquarium water changes and adjust as required.


Ammonia is the most toxic product formed in water. Sources of ammonia in aquarium water are fish respiration, digestion, and decaying foods. Freshwater fish begin to be stressed at levels of .50 ppm (parts per million). Marine aquaria levels should be less than .05 ppm; reef tanks at 0 ppm. Note that toxic ammonia converts to nontoxic ammonium when the pH is below 7.0. 2


Nitrite is the toxic intermediary product created in the process of breaking down organic waste products. It occurs between ammonia and nitrate in the breakdown sequence. Levels above 1.0 ppm are to be avoided in fresh water aquaria. Saltwater fish levels should also be maintained at less than 1.0 ppm; although this is not as critical due to nitrite not easily entering saltwater fish’s blood. Nitrite levels in reef aquaria should be 0 ppm.


Nitrate is a mildly poisonous end product of the breakdown of nitrogenous waste products in the aquarium. While thought to be harmless to MOST freshwater species, freshwater aquarium levels should not exceed 300 ppm. Less than 50 ppm is the desired level for saltwater aquaria. Reef tanks should be maintained at less than 5 ppm. High nitrate levels in both freshwater and saltwater aquariums will promote excessive algae growth. Note that “tap water” contains nitrate and many other harmful contaminates.


Chlorine is a chemical additive used to destroy bacteria and is in Charlotte tap water. It is lethal to fish above .2 ppm. A good brand dechlorinator will eliminate chlorine instantly and should be used when using water sources other than reverse osmosis or deionized water.


Hardness is a measure of dissolved calcium and magnesium salts in water. Charlotte tap water usually ranges from soft to medium hardness. This is ACCEPTABLE for MOST freshwater fish and plant species. If the water is too hard for your specific application (such as breeding certain species), simply mix it with RO or deionized water until the required hardness is obtained. Most hobbyists will not have to measure this particular water quality.

Alkalinity: Alkalinity is a numeric measure of the resistance of water to a change in pH as acid is added. The higher the number (i.e. 2 MEQ/L – 3.5 MEQ/L), the more resistant pH is to dropping. Marine tanks should have an alkalinity of 3.2 MEQ/L or higher.


Specific Gravity:

The specific gravity (or density) is the ratio of the amount of total dissolved salts in water when compared to pure water. Pure water has a specific gravity of 1.000. As more salts are added to the water, the specific gravity increases. Marine aquariums should have a STABLE specific gravity of 1.022 to 1.027 with a median value of 1.023 being best.


Calcium carbonate is the building block of coral skeletons, clamshells and calcareous algae. Hard corals, soft corals, clams, snails, scallops, shrimps, crabs, starfish, sea urchins, and some algae extract calcium from the water continuously. Reef aquarium levels should be at least 400 ppm.

Phosphates: Phosphate is a salt, commonly found in tap water, which serves as an algae nutrient. Maximum phosphate levels are 2 – 3 ppm with less than .05 ppm being ideal. Reef tanks should be maintained at less than .05 ppm. Charlotte tap water has a phosphate level of 1 ppm. 3


Gravel Vacuuming and Partial Water Changes 

  • Regular, periodic partial water changes are mandatory to maintain proper water chemistry. A 25% water change every two weeks is recommended. Smaller volume, more frequent water changes are even more beneficial. 
  • Fish respiration, fish digestion and the decay of uneaten food generate three nitrogenous compounds; ammonia; nitrite, and nitrate. The first two, ammonia and nitrite, are toxic to fish and extended exposure to them or introduction of fish to these compounds from non-contaminated water will result in disease and/or death. Nitrate is considered to be harmless to most fresh water species. At low levels it is stressful to saltwater fish; at high levels it can be toxic. 
  • In an established (cycled) WELL-MAINTAINED aquarium there are nitrifying bacteria present which will convert ammonia and nitrite into a relatively non-toxic compound (nitrate). Nitrates are best removed from the aquarium by performing partial water changes. There are also nitratereducing compounds which work well when utilized on a regular basis. 
  • When performing partial water changes, the gravel should be simultaneously vacuumed to remove trapped debris and uneaten food to insure an adequate oxygen supply to the nitrifying bacteria and to remove undesirable nutrients. 

Gravel vacuuming procedures:

  1. Unplug heaters, power filters, powerheads, and air pumps.
  2. Remove ornamentation other than live plants.
  3. “Walk” the gravel cleaner across the entire bottom of the aquarium, agitating the substrate in the gravel cleaning tube until the water being extracted is free of debris. If water is being removed too quickly to remove all the debris, pinch the gravel cleaner hose to restrict the water flow. If you have a plenum in your saltwater aquarium, only the top ½” of sand should be cleaned so as not to disturb the anaerobic bed.
  4. In freshwater aquariums add dechlorinator and aquarium salt per manufacturer’s instructions TO THE AQUARIUM based on the volume of water you are changing.
  5. Refill the aquarium with water of the SAME temperature and pH as that of the aquarium water.
  6. In saltwater aquariums, the replacement water must be dechlorinated, premixed, and prebuffered before being added to the aquarium. ALWAYS dechlorinate the water prior to the addition of sea salt. Some marine salts now include a dechlorinator in their ingredients. However, this dechlorinator is not uniformly distributed throughout and should not be relied upon as the sole source of dechlorination. Premixed saltwater should be aerated or otherwise agitated for 24 hours before being introduced into the aquarium to insure that the specific gravity and pH are correct. The use of RO or deionized water is highly recommended.
  7. Restart filters, powerheads, and air pumps.
  8. WAIT fifteen minutes BEFORE plugging the heaters back in.

There are specific circumstances that will somewhat alter the above procedures. These include:

  1. If the pH is extremely low, several small volume water changes (approximately 15% must be done twenty-four hours apart. A single, large volume water change will put the fish into pH shock, probably resulting in multiple fish deaths. This is particularly crucial if ammonium is also present. Raising the pH will chemically alter the ammonium increasing its toxicity by turning it into ammonia.
  2. DO NOT do gravel vacuum/partial water changes while the nitrification cycle is occurring unless you are experiencing multiple fish deaths. Water changes will lengthen the time frame for this required cycle to complete itself. The addition of Bio Booster is a must!!
  3. If your aquarium is not equipped with a Penguin or Emperor Bio Wheel system or an undergravel filter, gravel vacuuming and filter maintenance should not be performed at the same time. The consequent loss of a large percentage of nitrifying bacteria can cause temporary ammonia and nitrite related stress to the fish. These two functions should be performed at one-week intervals.
  4. Continually “topping off” aquariums to replace evaporated water increases toxicity concentration as toxins do not evaporate. Such water replacements do not constitute a water change.

Power filters, Powerheads, and Water pumps: 

  • Periodically remove the impeller. Clean the impeller and the impeller seating area to remove debris and slime coating, which will retard the electromagnetic field. 
  • Keep the intake strainer and/or prefilter clear of debris. 
  • NEVER restrict the intake flow of water. Any adjustments to flow rate must be made to the exhaust. 
  • Clean protein skimmer tops weekly (or as needed) to maintain a clear view of the operating level of the skimmer. 
  • Other specific maintenance per manufacturer’s instructions.

Filter Media: 

  • Disposable filter cartridges should be replaced monthly on an average stocked aquarium. Filters recirculate the same water over and over. Regardless of where particulates collect – whether it is the aquarium bottom or in the filter – they will be broken down to produce ammonia. Monthly replacement of filter cartridges will remove the particulate from the aquarium and keep the flow rate from slowing down due to clogging. This will also keep the carbon within the cartridge fresh. 
  • Reusable and/or biological filter media should be washed in water taken from the aquarium only if needed. This should not be needed on a regular basis. Chlorine in tap water is lethal to nitrifying bacteria, so DO NOT rinse the biological filter with tap water. 
  • Soaking in a solution of unscented household bleach and water (one part bleach to five parts water) for several hours should clean micron cartridges. Rinse thoroughly under pressure. As an added precaution, they can be soaked in a solution of water and dechlorinator prior to being reused. 
  • Chemical filter media; carbon, ammo carb and ammonia chips should be replaced each month. These media remove molecules of organic compounds from the water UNTIL the surface area becomes saturated. Once saturated, these media are no longer effective and may, in fact, begin releasing compounds back into the water. 
  • Several manufacturers now offer rechargeable chemical media as an alternative to carbon. These should be used and recharged in accordance with manufacturer’s instructions.

Important: If for any reason, the power filter has been shut off for two hours or less, biological, chemical and mechanical filter media should be thoroughly rinsed with aquarium water before restarting the filter. To preserve existing nitrifying bacteria, rinse the biological filter media with water taken from the aquarium. If the power filter has been off for more than two hours, the mechanical and chemical filter media must be discarded and the biological media thoroughly rinsed with aquarium water. Toxic anaerobic bacteria will be present which may cause fish deaths.

Air Pumps and Air Stones: 

  • Diaphragms and flapper valves have to be replaced periodically as symptomized by reduced output and/or noisy operation. 
  • If your air pump is equipped with a fibrous filter, replacing this filter regularly will greatly prolong pump life. 
  • The purchase of a supplementary battery air pump is highly recommended to prevent the loss of oxygenation during power outages.
  • Air stones eventually become clogged as evidenced by reduced bubbling and should be replaced to prevent the loss of nitrifying bacteria and damage to the air pump. Soak new air stones in water for several hours before installing them in the aquarium. 
  • Air stones in protein skimmers should be replaced every two weeks.

Aquarium Glass: 

  • Clean the exterior glass with a non-toxic aquarium glass cleaner and paper towels. Spray the glass cleaner onto the paper towel rather than onto the glass itself to prevent over spray into the aquarium. Do not use glass cleaners that are NOT specifically designed for aquarium use (i.e. Windex) as this may harm your fish. 
  • Clean the interior glass with an algae scrubber pad. Ideally, do this just prior to changing the filter media or doing a partial water change so that dislodged algae will be removed from the aquarium when the cartridge is replaced. Algae magnet cleaners are also available which will minimize your hand contact with the water. Never use algae pads for any other purpose in your home. 
  • Glass canopies should be cleaned regularly to provide maximum penetration of light.

Aquarium Lighting: 

  • Fluorescent tubes and starters should be replaced every twelve months in freshwater aquariums to provide maximum visual quality and plant growth. 
  • Fluorescent tubes should be replaced every six to eight months in marine aquariums to provide the correct balance of full spectrum lighting. Nuisance microalgae is the result of negative color shifts in the spectrum of light in aged bulbs. 
  • VHO tubes should be changed every five to six months. 
  • Power compact lamps should be replaced every ten to twelve months. 
  • Metal halide bulbs should be replaced every ten to twelve months with 20,000K bulbs replaced every six months. 
  • Maintain adequate lighting. Recent research indicates that the intensity of the light is even more critical than the duration. A single full spectrum bulb may be adequate for a ten-gallon (or other twelve-inch aquarium) but taller tanks need a higher degree of luminance. Some modern reflectors or hoods have the capacity to hold two bulbs. If this is the choice you make, we strongly suggest that two entirely different types of bulbs be used: a full spectrum bulb in front so that your fish show to their best advantage and a bulb more advantageous to plant growth in the rear.

Artificial Plants, Rocks, and Other Ornamentation: 

  • Surface algae and dirt can be removed by soaking the item in a solution of unscented household bleach and water (one part bleach to five parts water). Rinse thoroughly and soak briefly in dechlorinator (sodium thiosulphate) before returning to the aquarium. DO NOT soak driftwood in bleach. Scrubbing with a soft bristle brush can clean the surface. 
  • Be very cautious about using decorations found in local streams, rivers, lakes, oceans, or on land. These may have come in contact with fertilizers, petroleum products, or other toxins. To be safe, use these type items to decorate your home, not your fish’s home. 
  • Some medications consist of permanent dye base solutions. Remove porous surface decorations while medicating.

Live Plants: (Stan Makowski; Jermack Cultivated Plants) 

  • “Trim bunch plants before planting. Remove the weight, trim as many leaves from the stem as is practical, then replace the weight in a spiral fashion, but not too tightly. Some plants will survive without this simple procedure, but more often the leaves under the weight rot over the first week or two, and this causes the stem to deteriorate at the base and the rest of the plant to surface. When 6 planting rooted plants, it is critical that they not be placed too deeply in the gravel. The top of the root structure should be visible. Once established, live plants should be pruned periodically. 
  • Remember to use fertilizer. Most liquid fertilizers, in addition to replacing needed trace elements and nutrients, actually aid in changing mulm into substances that are more easily absorbed by the plant’s roots. A good quality liquid fertilizer may be adequate for a beginner’s aquarium or even one of small dimensions. However, those wanting optimum results would be wise to also purchase one of the many products that apply fertilizer directly to the gravel. Test kits are now available to test the iron level in the water. If phosphate is present (Charlotte tap water: 1 ppm), the available iron will chemically combine with the phosphate forming a compound which is insoluble by the plants. An iron deficiency condition known as iron chlorosis may result. The plants turn yellow and the leaves and stems both become very brittle. Fertilizers containing iron supplements will correct this condition. 
  • Filtration. Avoid an undergravel filter if at all possible. For reasons not yet completely understood, undergravel filters appear to inhibit aquarium plants form absorbing certain vital nutrients. As a result, plants may become stunted and pale yellow in color, indicating that photosynthesis is somehow disrupted. If you already have an undergravel filter and do not want to remove it, consider leaning heavily on potted plants. Also to be avoided in heavily planted aquariums are devices, which would enrich the water with oxygen and/or cause carbon dioxide to escape. These include power filters whose return flow causes heavy surface turbulence and airstones. Trickle filters are also not recommended, as the filtered water contains almost no carbon dioxide.


DO NOT OVER FEED. Unless your fish are highly specialized feeders or have a very high metabolism (i.e. yellow tangs), feed your fish once daily and only what they will completely consume in 1 – 2 minutes time. To insure adequate nutrition, provide a varied diet and use vitamins on the food at least twice a week. Uneaten food should be removed from the aquarium if not eaten with 5 minutes. Contrary to many manufacturers’ claims, overfeeding will result in cloudy water, excessive algae growth and deteriorating water quality.


Thank you for taking the time to read this handout. We trust that it will serve to answer most of your questions as they arise. Hopefully, it has not left you with reservations that successfully maintaining an aquarium is an arduous task. Nothing could be further from the truth. Primarily, it is a matter of common sense. Fish, and other aquatic inhabitants, cannot survive in polluted water. Take a few moments each day (feeding provides an excellent opportunity) to observe that everything in the aquarium is functioning properly. Evaluate the overall condition and appearance of the fish and other inhabitants. Remove any uneaten food material or other debris on the substrate and/or ornamentation and remove any water spotting on the glass or aquarium trim. If the fish appear to be behaving abnormally, make the appropriate tests to insure proper water quality and look closely to see if there are any visible signs of disease. Twice a month devote the small amount of time required to perform partial water changes and gravel vacuuming, service the filters as required, scrape algae from the glass and check water quality. The result will be a trouble free, long term successful aquatic experience. ENJOY

Leave a Reply

Your email address will not be published. Required fields are marked *