How to Correct Soft Water in a Freshwater Aquarium

Aquariums allow people to collect fish from around the world to display and keep in their homes. Yet water sources available may not always have the same qualities as the water the fish are naturally accustomed to. One of these components is the water's hardness, which measures dissolved minerals in the tank. If a freshwater aquarium has low mineral content, it's considered soft and could be stressful to your fish. Correct soft water by understanding how hard it needs to be for your fish and adding necessary chemical to make it harder.

Things You'll Need

  • Water hardness test kit
  • Non-phosphate alkaline buffer
  • Epsom salt
  • Calcitic gravel
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Instructions

    • 1

      Determine how hard your tank's water needs to be for the specific fish living in it. Water hardness is a combination of many factors, including the water's calcium, magnesium and other chemicals' makeup. Every species require different levels. For example, an African cichlid needs a general hardness between 160 to 320 parts-per-million.

    • 2

      Measure your fish tank's water hardness. There are general hardness water test kits that can be purchased at fish stores. Each kit is different, so follow the directions. Once you know how hard your tank's water is, determine how much harder it needs to be for your fish's needs.

    • 3

      Add a non-phosphate alkaline buffer to your aquarium's water. These chemicals will work to harden soft water. This buffer can be purchased from a fish store, and should be used as directed. You can also create your own buffer. Using epsom salt, add 1 milliliter to every 10 liters of tank water to increase the water's hardness by 70 mg/L of calcium carbonate.

    • 4

      Add a calcitic gravel to your aquarium to further combat soft water. This compound is usually made of organic materials naturally found in water beds, such as crushed coral or aragonite sand. This substrate will slowly break down over time, which will add calcium carbonate to your water and increase the water's general hardness.