Jan
25

Deionized Water For Reef Users

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Background

Reverse osmosis deionization units (RO/DI) are essential in the successful management of a reef tank. These units provide ultra pure water for a stable, predictable reef environment. The purified water allows the reef aquarist to determine and add only the essential trace elements and other essential nutrients to the water without any other unwanted metals or organic impurities.

What is Deionization?

It is the removal of mineral ions by using the ion exchange process. Using a mixed bed of anion and cation resins; ions, salts and minerals can be entirely removed from water.

How long does DI last — What is its life?

The RO membrane has a direct impact on the life-span of the DI. The RO membrane can remove about 95-98% of TDS (minerals) in your water. When a DI is used after the RO membrane, you can expect almost 100% removal of the TDS.

On average, a pound of DI resin will have a life of approximately 600 gallons of water when the DI housing is installed after a RO system.

There are some exceptions to the amount of gallons that can be treated by a pound of DI resin. Higher than usual levels of some TDS can cause the DI to exhaust faster.  Some examples of elements that, if in high levels, can cause the DI to exhaust faster are: phosphates, nitrates, silicates, salt, calcium, etc. The RO membrane can remove most of it, but the DI would have to work harder than usual to remove it all from the water. If the unit has been inactive for more than one day, this will also cause the DI to exhaust faster.

Benefits Of Deionization Process

So why does the water need to go through a DI filter? The water goes through this extra process to remove any ions left in the water after the RO system. Some ions are small enough to pass through the semi permeable membrane so the water then they must pass through a deionization filter which contains both cations and anions to remove the remaining contaminants.

RO/DI units are an investment for the reef owner but they save the reef aquarist the hassle of purchasing purified water from grocery stores or their local fish store which is more expensive and sometimes questionable in terms of purity. RO/DI units are another useful piece of equipment in a successful reef tank.

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