Water Chemistry

You do not need a Ph.D. in Chemistry to understand aquarium water chemistry.  Most of what you need to know is pH, dH (hardness), salinity, and a little bit about the nitrogen cycle which relates to ammonia levels in aquariums.  

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   Under an assumption that many visitors to this section are new hobbyists or those wishing to take some next steps we're not going to make this any more technical or complicated than necessary.  Basically it boils down to what to test for, how often and the wisdom for weekly water changes. Test kits which can be obtained on-line, or at a local pet shop, ultimately prove cheaper than fish.


    The best prevention and remedy for high levels of ammonia, nitrates, nitrites and other chemicals, is a regular weekly 10% water change.  I also recommend that as you let your water sit to remove chlorine from tap water that you add a little aquarium salt to this water.  Please note, if you only add water that was evaporated, DO NOT add more salt, because salt does not evaporate and you will then be raising the salinity of your water over time.  I usually add about 1/3 to 1/2 tsp. of aquarium or seasalt to a gallon of water I am replacing.   Aquarium salt or seasalt also contains the minerals and trace elements that fish need to thrive.   Even freshwater fish need some salt in their water.  I would also add a little white vinegar, if I am using tap water, because I've found that most city water has a pH of 7.8, which is alkaline.  I add the vinegar to lower the pH to about 7.0 - 7.2. 


    I likewise add my aged replacement water over a period of about 10 min, certainly for my more sensitive fish.  You'll find this weekly practice of replacing 10% of the water in your aquarium is the best thing you can do to insure the health, color and reproductive viability your fish.  God gives the fish water changes, it is called rain!  One of the most common 'tricks' that fish breeders use is a water change to induce spawning.  A gallon of bottled water (certainly soft water) or distilled water is fine to use, but isn't absolutely necessary, unless you are trying to spawn difficult fish, who require soft water.


    In a newly set up aquarium, water testing is a must.  First to see what conditions you have and to prevent the usual 'new tank' fish loss, because ammonia, nitrites, and other variables rapidly rise.   Another common 'new tank' experiences is that once fish start dying, anaerobic bacteria (the type that make the tank stink) rise as there are not sufficient population of aerobic (air breathing) bacteria to keep the anaerobe populations down.

    Even in an established tank, water testing is necessary to promote the color, breeding and general health of your fish.   As you know different species of fish come from different areas of the world, different climates and different water conditions. The links to the fish on the right, describes some of these conditions.


 Test kits can either be obtained at your local pet shop or on-line here and you'll find they are really very simple and inexpensive.  Certainly cheaper than a tankful of fish.  If you really aren't sure, visit your local fish shop and ask them to test your water.  Some charge a nominal fee

    So what do you test for?   The tests I've found most useful to the average hobbyist (certainly for those wishing to breed fish) are Ammonia, pH, Nitrite, and Nitrate.  Salinity and hardness levels should also be considered, but if you do weekly water changes of 10% or more and replace the aquarium salt to cover the amount removed per gallon (marine/saltwater fish are different per salinity concerns) you shouldn't really need to worry about these too much.. It is a good idea, certainly if you wish to maintain more than one aquarium, to keep a log for your aquarium writing down such things as testing levels, number of fish, condition of fish, spawns, etc.


pH
 pH is the the measure of how acid, neutral or alkaline the water is.  7.0 is neutral and anything less is acidic and anything over 7.0 is considered alkaline.  This is an important water chemistry consideration for the health of your fish and it is crucial if you wish to encourage them to spawn. Fish cannot tolerate sudden changes in pH. Even a small change of .2 can result in stress or even death if it occurs suddenly.  When you add fish slowly to the aquarium after bringing them home, after you've let the water temperatures equal, you do this slowly to slowly change the pH.   pH will change with time. Fish and plant waste, water evaporation, water addition, and other populations of organics will effect changes in the pH.


Water Hardness
    Water hardness refers to the amount of calcium and magnesium salts present in the water. Too much hard water causes a white crust to form on parts of the aquarium. Hard water makes it difficult to adjust the pH. Products are available to help soften the water. You can also lower water hardness by using soft bottled water or distilled water.

Salinity
    Although salt is associated with marine aquariums, freshwater aquariums can benefit from small doses, as well. A lack of sodium (salt) in the water will break down the slime coat of fish. One tablespoon per five gallons will provide enough salt for most fish. Mollies, Swordtails, Tetras, Fancy Guppies, and Goldfish prefer a little more. Cichlids, Knifefish, and Ghosts prefer less. Only use salt that is recommended for aquariums. Never use regular table salt which may contain iodine.


Chlorine and Chloramine
    Chlorine is found in most tap water and must be neutralized with a water treatment that removes chlorine.

    Chloramine is a combination of chlorine and ammonia. It is a stronger disinfectant than chlorine alone and is used in areas where this extra disinfection is needed. You can call your local water department to find out if chlorine and chloramine is in the water, or you can buy a Chloramine/Chlorine test kit at your local pet shop or on-line through some of our recommended pet shops

Ammonia
    Testing for ammonia is one of the fundamental tests of aquarium water. Ammonia will be higher during a new tank cycle, but can also increase in established tanks if the water is not changed regularly, filters are not kept clean or become clogged, if their are too many fish, or if medication is used that disrupts the biological cycle, such as an antibacterial agent killing off large aerobic (the good kind) bacteria. In an established tank, an ammonia test should be performed and recorded in a log once a month. Anytime you have sick fish, or a fish death, you should immediately test for ammonia.  This is certainly true, if you loose your scavenger/catfish or others that inhabit the lower strata of the aquarium.   At concentrations as low as .2-.5 ppm (for some fish), ammonia causes death   Even at levels above 0.01-0.02 ppm, fish will be stressed.   If the ammonia is a problem it must be dealt with immediately with a 20% change of aged water to reduce the toxicity and harm to your fish.


Nitrite
   During the startup of a new tank, Nitrite, as is true of ammonia, levels will soar and can stress or even kill fish, as the aquarium's cycles begin to establish themselves. However, even after an aquarium is initially cycled, it is not unusual to go through mini-cycles from time to time, just as populations of fish cycle. When you do your monthly testing, include nitrite testing as part of the routine. Any elevation of Nitrite levels is a red flag that indicates a problem brewing in the tank. If a fish is ill, or dies, it's wise to test for Nitrite to ensure that is not contributing to the problem. The only way to reduce elevated Nitrite levels quickly is via water changes.

Nitrate
 Although Nitrates are not as toxic as Ammonia or Nitrites, they must be monitored to avoid stressing the fish. Nitrates can also be a source of algae problems. Nitrates will rise over time and can only be eliminated via water changes.  Monthly tests are important - particularly when breeding fish, as young fish are more sensitive to Nitrates than adult fish.  Test monthly and keep levels low to ensure a healthy tank.

Phosphate


 If your aquarium is prone to rapid growths of algae, excessive light and phosphate levels are usually factors. Phosphates serve as a nutrient for algae. If your phosphate levels are high, check the dry fish food you are using, since general feeding, emphasis overfeeding, with lower quality foods high in phosphates, will raise these levels in your water over time.. If algae is getting the better of you, test for phosphates, reduce the amount of light, emphasis direct sunlight and take the more natural approach to eliminating algae by getting a scavenger (i.e. Chinese Algae Eater), rather than add more chemicals to the water.

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