Adjusting Water Chemistry (Cont.)
Deionization filtration units are sold by some aquarium product manufacturers. They use a positive and a negatively charged resin to remove elements from the water. These type of filters can get exhausted very quickly, especially if you have very hard tap water. Many aquarist use DI filtration systems after a RO filtration system to remove the final dissolved solids.
Ion exchangers are available by some aquarium product manufacturers, often called water softening pillows, but they exchange calcium and magnesium for salt (sodium chloride), and do not give the ultimate desired result of lower TDS. Water softening pillows are recharged by soaking it in saltwater. Whole house water softeners are also an example of an ion exchanger that also is recharged with salt.
For aquariums 10 gallons (38 l) or less, store bought distilled water may be another solution to consider. Distilled water has no hardness and is excellent for hatching eggs of soft water dwarf cichlids.
Many species of freshwater fish that come from hard and alkaline water conditions will do much better if you supply the same water chemistry in the aquarium. Fish that have evolved in these conditions will often become susceptible to bacterial infections if the same conditions are not provided in the aquarium. Often freshwater fish that some hobbyist have label as “hard to keep,” is do to not providing the proper hardness and alkalinity. Fish that come from Lake Malawi, Lake Tanganyika, Lake Victoria, Caribbean/Gulf Coast side of North, Central, and South America, will often benefit from adjusting the hardness.
How much you will need to adjust the hardness will be directly related to the hardness you are starting with from the source water. Local municipal water suppliers will often publish water chemistry analysis reports on the internet that you can view. These reports will show how many ppm of the elements in the water make up the TDS. You should also test your source water and then adjust accordingly.