How to Keep Live Plants & Fish With Reverse Osmosis Water

Reverse osmosis is a filtration process that removes nearly all contaminates from water. Reverse osmosis (RO) water is excellent for tropical freshwater fish and live plants. That RO water is so pure is both an advantage and a disadvantage in that the filtration process removes some nutrients that plants need to thrive. However, these nutrients can be added to the aquarium in measured amounts as supplements.

Things You'll Need

  • Reverse osmosis filter
  • Total dissolved solids (TDS) meter
  • pH adjustment drops
  • Carbonate hardness (KH) adjustment powder
  • Aquatic plant fertilizer
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Instructions

    • 1

      Install your reverse osmosis filter. Each brand of filter is slightly different, but generally the inlet will attach to your home water supply by screwing onto the faucet or with a saddle screw that attaches to the water pipe. Attach the filter to the cold water pipe. You will have two outlet tubes from the filter: One is for the purified RO water and the other is "waste" or unfiltered water. It is a good idea to use different color tubes for each so you can easily identify them.

    • 2

      Filter the tap water using the RO filter. The purified water will come out as a fast drip and the unfiltered water will come out much faster. It will take several hours, perhaps even over night, to fill a bucket with purified water. Pay attention to the filtration rate as you can easily flood a room if you forget to check the water level in the bucket. Some RO units come with a float valve that will shut of the filter when the water level reaches the desired height.

    • 3

      Measure the total dissolved solids in the RO water. You can find total dissolved solids (TDS) meters at some aquarium hobby stores and online. These meters indicate how pure the filtered water is by measuring the other solids present. Ideally, you want a reading of 0 but below 3 is usually acceptable. If the TDS starts to raise, you will need to change your RO filter.

    • 4

      Adjust the RO water's pH and hardness to your desired level. The pH of the RO water should be 7, which is neutral. This is acceptable for most freshwater aquariums; however, discus need a pH between 5 and 6.5. Carbonate hardness (KH) is related to pH and is also important to the aquarium. RO water typically has 0 dKH (degrees of carbonate hardness) and most fish will need higher levels. You can purchase water hardener compounds in aquarium stores.

    • 5

      Add the RO water to the aquarium. The chlorine is removed in the RO filtration process, so there is no need to add dechlorinators.

    • 6

      Add tropical plant fertilizers to the aquarium water. Live plants need iron and phosphate to thrive in the aquarium. The reverse osmosis filtration process removes these elements and they need to be added back. The advantage of adding this yourself is that you can control how much and what goes into the aquarium.