A Reverse Osmosis Unit or RO/DI Unit, is a system that filters your tap water and removes all the impurity’s from the water. Most people in the aquarium hobby use RODI Units for saltwater aquariums, as they are very beneficial to have. With A saltwater aquarium when you add water to the aquarium the water needs to be perfect and pure and the RODI unit does just that. RODI units can also be used for freshwater aquariums, you just need to make sure you use it correctly.

I’ve recently purchased a “5 Stage Premium 75 GPD RO/DI System” From Bulk Reef Supply and it works great! Its probably filtered through around 100+ gallons of water for me so far with no issues. I purchased the Premium Unit so it comes with a few bonus tools. It has a TDS Meter on top of the DI resin container, which shows the total dissolved solids coming in and going out of the unit. It has a gauge on the top right of the system to show the water pressure coming into the unit. Along with a flush valve which flushes out the Membrane on the unit and removes any built up material inside the membrane and improves the longevity of the unit.

The stages of which the Water filtering process works starts with the Sediment Filter (the first stage/container), Sediment filters trap debris and other free-floating particles in the water. Next you have your carbon block (second stage/container), Carbon blocks remove and reduce chlorine and volatile organic compounds from household water. The third stage is the RO Membrane, the membrane is the white tube at the top of the container. The RO Membrane removes things like dissolved salts, minerals, heavy metals, bacteria, viruses, and organic compounds. Last but not least is the fourth stage (third container), which is the DI resin or Deionization stage. The DI resin inside of the third container will polish your water down to 0 TDS, and is usually color changing to let you know when it needs to be changed.

As much as RO/DI units are targeted to saltwater aquariums, freshwater keepers can use them too. With saltwater people use the RODI pure water as top off water or as water to mix with salt. But for freshwater using pure RODI water is not exactly good for the fish because they need minerals in their water. If you want to use RODI water for your freshwater aquarium the best way to do it is to remineralize the water. There is a lot of products out there to remineralize RO water, the Line of products I personally use Seachem Equilibrium, Seachem Alakaline Buffer, and Seachem Acid Buffer.

If you want to learn more about RO/DI Units or have any question about fishkeeping let me know in the comments below.