How to Use Softened Water for Fish Tanks

Soft water contains very few dissolved minerals. Under natural conditions, soft water is found in rivers and tributaries which flow over ground that is poor in minerals. These conditions typically exist in rivers that flow through West Africa, South America and Southeast Asia. Many of popular aquarium fish species originate from these rivers, but creating and maintaining soft water is a challenge. Select fresh water species will only thrive and breed in soft water though, and aquarists who keep these types of fish need to use soft water in their aquariums.

Things You'll Need

  • Reverse osmosis unit
  • Test kit to measure general hardness
  • Water softening pillow
  • Test kit to measure pH of the water
  • Buffer agent to lower the pH of the water
  • Peat granules
  • Nylon bag
  • Plastic cable tie
  • Canister or hang on filter
  • 10-gallon plastic container
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Instructions

    • 1

      Attach a reverse osmosis unit to a kitchen or outdoor tap.

    • 2

      Turn on the unit and collect sufficient water to fill your aquarium to the three-quarter mark. Fill the remaining quarter of the aquarium with tap water.

    • 3

      Add an aquarium heater and power head to circulate the water. Allow the water to circulate and heat for at least a day.

    • 4

      Test the general hardness of your water by using an aquarium hardness test kit. Use an aquarium "water softening pillow" to lower the general hardness to between 50 and 100 ppm.

    • 5

      Test the pH of your water by using a pH test kit. If the water measures a pH of 7 or above, add an appropriate buffer agent to lower the pH. Add buffer as per instructions on the container until the pH measures 6 or slightly below. Soft water fish are most comfortable in water with a pH of 5.8 to 5.9.

    • 6

      Pour a cup full of peat granules into a nylon bag. Seal the bag with a thin plastic cable tie. Briefly rinse the nylon bag under a running tap, to remove any dust.

    • 7

      Place the nylon bag into the chemical filter compartment of your canister or hang on filter. The peat will assist to keep the pH of the water in the optimal range. Plug the filter into a power source and turn on.

    • 8

      Replace approximately 10 percent of the original water on a weekly basis. Add a commercial liquid peat extract to the container holding any new water, before adding it to the aquarium.