Mastering Freshwater Aquarium Ecosystems
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Adjusting Water Chemistry (Cont.)

The two main elements used to make water hard are calcium and magnesium. Beware that calcium and magnesium do not evaporate and should normally only be replaced when doing a water change. Top off water does not need additional supplementation unless you need to raise the hardness level of the aquarium.

There are several ways you can add calcium to the water. Calcium chloride (Pool Calcium Hardness Increaser, Kent's Marine Aquarium Turbo Calcium, Dow Flake) is a dry chemical, when added to water heats up as it dissolves. It should always be dissolved in a container outside the aquarium before being added. You should keep a log of how much calcium chloride you are adding to the aquarium, and how much it raised the TDS or GH. You can use the information you gather in determining how much you need to add to the aquarium when doing water changes.

Other sources of calcium that can be used are liquid calcium marketed to marine aquarium hobbyist by manufacturers. Liquid calcium is not as concentrated as calcium chloride, so you will have to use more to reach the desired target.

Adding 1 teaspoon of calcium chloride per 10 gallons (4 liters) will raise the TDS approximately 100 ppm

Magnesium can be increased by adding magnesium sulfate (epsom salt) or magnesium chloride. Magnesium levels will need to be increased if you notice calcium precipitating out of solution. Calcium and carbonate can combine and fall out of solution when magnesium levels are too low. This can cause the pH and hardness to drop. Magnesium chloride is the preferred chemical to use to raise the magnesium level, but epsom salt can also be used.

Hardness Increasers

Magnesium sulfate (epsom salt) and calcium chloride (pool hardness increaser) are are used to increase hardness in aquariums. Epsom salt is available in most grocery stores, and calcium hardness increaser can be found in pool supply stores.

Adding 1 teaspoon of magnesium chloride per 10 gallons (4 liters) will raise the TDS approximately 70 ppm.

Some aquarium product manufacturers make pre-mixed salts for increasing hardness. Seachem makes a “Cichlid Lake Salt” that is a good product for those hobbyist that are trying to keep fish that come from Lake Malawi, Lake Tanganyika, and Lake Victoria. Seachem's “American Cichlid Salt” can be used for livebearers also, like mollies, platies, swordtails, variatus, and guppies. Kent Marine also makes some products to help raise hardness in freshwater aquariums.

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