Tap Water Purification for Aquariums. R/O Reverse Osmosis

Water changes, though important in the regular maintenance of an established aquarium, can introduce unwanted impurities such as phosphate, nitrate, chlorine, copper, etc. Using reverse osmosis water for water changes can eliminate these unnecessary additions.

There are plenty of water conditioners available, but none will provide water as pure as a reverse osmosis unit. Depending on the type of reverse osmosis system used, up to 99% of impurities in tap water will be removed. Used in combination with a deionization filter, the tap water gets filtered as close to purity as possible.

Reverse osmosis filters work by pushing the water from the tap through a semi-permeable membrane, removing impurities. The amount of what is removed depends on the type of membrane used. Cellulose tri-acetate membranes, used only for chlorinated water due to its tendency to break down with exposure to bacteria, will remove between 88 and 94 percent of impurities. Thin film composite membranes, also referred to as thin layer composite membranes, can remove between 94 and 98 percent of impurities and require the water to also run through carbon and sediment filters to remove chlorine and finer particles. High removal membranes, especially used for the removal of silicates, will take out between 97.5 and 99 percent of impurities.

Chloramine, a chemical used by some municipal water systems, is not easily broken down by some membranes, though there are units that offer a catalytic carbon filter which will break the chloramine into chlorine and ammonia for removal. In other words, it is best to know what is in the water before purchasing a system to purify it. AquaLife Complete will insure tap water that contains chloramine is safe while reducing fish stress and preventing disease.

Another important selling point for reverse osmosis units is the amount of water a unit wastes in the process of purification. If the unit wastes five gallons of water to every gallon, then the unit may not be considered very cost effective, especially since higher end aquarium stores usually sell reverse osmosis water. Reverse osmosis sytems work more efficiently under high pressure. If a pressure gauge is used, the recommended water pressure is between 50 to 125 pounds per square inch.

Sediment and deionization filters need to be replaced when the filter becomes visibly dirty, which is generally once every three to six months. It is a good idea to change the carbon filter at the same time. The semi-permeable membrane should be replaced approximately every 18 months, though a total dissolved solids meter can more accurately determine the need for changing. Another option is testing every 100 gallons of water with a chlorine test.

Terms you should know:
Cellulose tri-acetate membrane. Used in reverse osmosis systems to filter impurities from water, this semi-permeable membrane is susceptible to degradation by bacteria. It should be used only with chlorinated water.
Chloramine. Many municipal water systems use chloramine instead of chlorine to treat drinking water, and chloramine can wreak havoc with some reverse osmosis sytems. An activated carbon fitler can remove chloramines from water before it hits a reverse osmosis system.
GPD. Gallons per day.
High removal membrane. Used in reverse osmosis systems, this semi-permeable membrane removes up to 99 percent of impurities from water and is especially useful for removing silicates.
Microns. The measurement for the minimum particle size a filter will remove. Filters with lower micron numbers will filter out more particulate matter.
PSI. Pounds per square inch.
RO. Reverse osmosis.
RO/DI. Reverse osmosis with deionization.
TFC/TLC membrane. Another semi-permeable membrane used in reverse osmosis sytems, the thin film composite membrane, or thin layer composite membrane, works equally well with chlorinated and non-chlorinated water.
TDS. Total dissolved solids, or the impurities that reverse osmosis removes from water.
VOCs. Volatile organic compounds.



AquaLife Barracuda
Supplier: Aqua Engineering & Equipment
System Type: An RO/DI system that yields laboratory-grade water in most instances. Available in 100, GPD flow rates.
Filters: Uses a high-flow/high-rejection Dow TFC membrane, a high-efficiency 1-micron sediment filter, a 2-micron carbon block filter, and a high-efficiency color-changing DI resin cartridge.
Features: Includes 160 PSI pressure gauge, inline TDS meter, clear 10-inch filter canisters, quick-connect fittings, shut-off valve, filter cartridge wrench, and choice of feed adaptor.

AquaLife Stingray
System Type: A portable RO system primarily used for backup or as a temporary source of pure water. Suitable for freshwater aquariums.
Filters: Uses a Dow TFC membrane and a 2-micron carbon block filter for chlorine and sediment removal.
Features: Includes quick-connect fittings, shut-off valve, filter cartridge wrench, and choice of feed adaptor.

Kent Full Size TFC RO
System Type: A full-size RO system that removes up to 94% of impurities from chlorinated or non-chlorinated water. Available in 24, 50, and 100 GPD flow rates.
Filters: Uses a TFC membrane (two in the 100 GPD model), a 1-micron sediment filter, and a carbon block filter.
Features: Includes clear filter canisters, garden hose adaptor, and 6 feet of yellow, blue, and orange tubing.

Ref. Bolch, Matt. �Purifying Water with Reverse Osmosis� Pet Age. July 2007, pgs.42-46