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Why You Should Use RODI Water for Your Aquarium.

Updated: Nov 25, 2023


RODI filtration System

Water quality is paramount for the health of your aquarium. This starts with adding only the purest water to your aquatic system(s). Reverse osmosis deionized (RODI) water is the product of pushing regular tap water though multiple high pressure filters.


RODI Filter Stages

This setup in my basement runs tap water at a pressure of 80 pounds per square inch (psi) through seven stages of filtration.


  • The first filter removes sediment at 1 micron.

  • The second and third filters remove toxic chlorine, chloramines and volatile organic compounds using high-quality catalytic active carbon.

  • The fourth filter is an ultra fine reverse osmosis membrane that removes up to 99% of the remaining contaminants from the tap water.

  • The fifth and sixth filters are cation and anion color changing deionization resins designed to polish the nearly pure water to bring the total dissolved solids (TDS) down to 0%. The color changing aspect of this filter helps you know when to change it.

  • The seventh and final filter is a mixed bed (cation and anion) deionization resin. This final stage is designed to catch any remaining contaminants that make it through the cation and anion resins.


Use RODI Water for Freshwater and Saltwater Aquariums

RODI water is very important in any aquarium, not just saltwater or reef tanks. Starting off with the "blank slate" that is RODI water allows you to create the perfect environment for your fish, plants, or coral.


The water from our taps in Kansas City is "hard". This means it is high in calcium and or magnesium, in our case calcium carbonate (limestone). This type of water is ideal for African cichlids, but is unhealthy for South American species where the water is naturally softer. Fish can adapt, but they will never be as healthy or as colorful as in their ideal water parameters.


Tap water also includes dozens of chemicals and additives that make it safe for us to drink, but would never be found in natural bodies of water, and are harmful to corals. Tap water also contains increased amounts of nitrogen, ammonia, silicates, and other compounds that can increase algae growth. Using RODI water to make new water for your water changes may require an extra step or two, but it will actually make maintaining your aquarium easier in the long run.


Creating the perfect environment with RODI water can be as easy as adding a pH buffer and a remineralizer. It can also be as complicated as titrating in specific amounts of dozens of different elements all of which have complex reaction relationships with each other. Regardless of how you mix your aquariums' perfect water, the health, longevity, activity, and beauty of your aquarium species will unmistakably benefit.

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