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Like all living creatures, fish give off waste products. These nitrogenous waste products break down into ammonia (NH3), which is highly toxic to most fish. In nature, the volume of water per fish is extremely high, and waste products become diluted to low concentrations. In aquariums, however, it can take as little as a few hours for ammonia concentrations to reach toxic levels.
How much ammonia is too much? The quick answer is: if a test kit is able to measure it, you've got too much. Consider emergency action (water changes and zeolite clay) to reduce the danger.
The nitrogen cycle, more precisely, the nitrification cycle, is the biological process that converts ammonia into other, harmless nitrogen compounds. Fortunately, several species of bacteria do this conversion for us. Some species convert ammonia (NH3) to nitrite (N02-), while others convert nitrite to nitrate (NO3-).
So, cycling the tank refers to the process of establishing bacterial colonies in the filter bed that convert ammonia -> nitrite -> nitrate.
Rapid pH changes stress fish. Tank water has a natural tendency to become acidic due to the production of nitric acid (nitrates) from the nitrogen cycle. Keeping pH stable requires having adequate ``buffering''. If your water is soft, you may need to add buffering agents. All of these products are readily available in your local pet stores.
General hardness (GH) refers to the dissolved concentration of magnesium and calcium ions. When fish are said to prefer soft or hard water, it is GH (not KH) that is being referred to.
Fish produce toxic wastes (ammonia) that must be broken down by bacteria through *biological filtration. Most fish deaths for first-time tank owners are a direct result of not understanding the nitrogen cycle and are completely avoidable. Regular testing of the water can avoid these fish deaths.
Hardening Your Water (Raising GH and/or KH)
The following measurements are approximate; use a test kit to verify you've achieved the intended results. Note that if your water is extremely soft to begin with (1 degree KH or less), you may get a drastic change in pH as the buffer is added.
To raise both GH and KH simultaneously, add calcium carbonate (CaCO3). 1/2 teaspoon per 25 gallons of water will increase both the KH and GH by about 1-2 dH. Alternatively, add some sea shells, coral, limestone, marble chips, etc. to your filter.
To raise the KH without raising the GH, add sodium bicarbonate (NaHCO3), commonly known as baking soda. 1/2 teaspoon per 25 gallons raises the KH by about 1 dH. Sodium bicarbonate drives the pH towards an equilibrium value of 8.2.
How much buffering does your tank need? Most aquarium buffering capacity test kits actually measure KH. The larger the KH, the more resistant to pH changes your water will be. A tank's KH should be high enough to prevent large pH swings in your tank over time. If your KH is below roughly 4.5 dH, you should pay special attention to your tank's pH testing weekly, until you get a feel for how stable the pH is. This is especially important if you neglect to do scheduled partial water changes. The nitrogen cycle creates a tendency for an established tank's pH to decrease over time. The exact amount of pH change depends on the quantity and rate of nitrates produced, as well as the KH. If your pH drops more than roughly two tenths of a point over a month, you should consider increasing the KH or performing more partial water changes. KH doesn't affect fish directly, so there is no need to match fish species to a particular KH.
There is a seemingly endless array of test kits for testing everything from ammonia levels to phosphate levels. It is quite possible to have a healthy tank without ever buying a single test kit, however, test kits are extremely useful at eliminating guesswork when something goes wrong.
The essential test kits you will need are: pH, ammonia and nitrate. In addition to those which I would consider necessary there are a few that are good to have: chlorine/chloramine, nitrite and water hardness.
Reverse osmosis is a process for filtering tap water before it is used in an aquarium. This process generates water slowly and wastes a couple of gallons of water for each gallon of filtered water produced. However it is one of the easiest home methods.
Basic water chemistry is pH, hardness and buffering. You don't need a chemistry degree, but you should know enough about water chemistry and the specifics of your local water supply so that you can keep fish happy. Every location's water source is different, and some fish won't be able to survive in your water. You can learn details about your water from a local fish store, or through the use of test kits.
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Lynne Christen |