Chloramine is a chemical used to disinfect water. It is ammonia (NH3) bonded to chlorine. It resists breaking down and is used because of its stability in water. Sodium thiosulfate on its own, can be used to remove the chlorine, but when used alone ammonia is left over. The toxicity of ammonia will depends on a few factors. This article should help you decide the best course of action in your situation. Ammonia is not toxic at a pH below 7.0. This happens because in acid conditions, free hydrogen ions convert it to ammonium NH4. As pH rises above 7.0, these hydrogen ions are less available, leaving more toxic ammonia (NH3).
Chloramine Removal: Chloramine can be removed in several ways. You can purchase a product like No-Ammonia, but it can be fairly expensive if you are dealing with a large hatchery and frequent, large water changes. No-Ammonia creates a chemical bond with ammonia that is synthesized by nitrifying bacteria. Items like zeolite will also remove ammonia, but its effectiveness is limited and not the best solution in most situations. You can also remove the chlorine, with very inexpensive sodium thiosulfate and deal with the ammonia separately.
Removing Ammonia Separately: If you decide to use sodium thiosulfate to remove the chlorine and deal with ammonia on its own, then the following will explain what to try. Nitrifying bacteria will convert ammonia to non-toxic ammonium. If your biological filter is a good one and the fish load is not too high for the filter, it may be all you need. Its effectiveness will vary depending on pH and fish load. To find out if your filter can handle the ammonia load, get a good ammonia test kit, do small water changes and carefully observe what happens. Start out with 5% water changes and increase them 5% at a time, until you see that the ammonia level is stressing the fish. At the level you can observe stress, you should cut back about 10% on the amount of water changed. With this method, you will probably never be able to do more than 30-40% water changes. If you're restricted to a small percentage, then you will have to do water changes more frequently than you would otherwise. If stress is seen at all levels, you will have to increase your aeration and biological filtration or resort to chemical removal of ammonia. The best course of action to remove ammonia will depend on your water's pH, the amount of ammonia in the water, the fish load and the size and efficiency of your biological filter. In my opinion, most situations can be handled with sodium thiosulfate and separate ammonia removal. You can decrease fish loads, increase biological filtration and even go so far as to lower pH. Some go through the effort of adding large amounts of reverse osmosis water to lower pH. You can also increase filter efficiency by installing oversized, high flow rate trickle filters that expose water for optimum gas exchange and biological filtration. It's worth doing all this, not only to avoid chemical removal of ammonia, but because it generally provides better conditions for your fish. This results in faster growth, more color and more beautiful fish.
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