As you get deeper into the world of marine aquariums, you quickly realize that the happiness of your organisms depends on the quality of their water. You might be tempted to pour tap water into your aquarium, since it’s convenient and cheap. But, depending on whether your water comes from a municipal source or from a well in the back yard, it can have too high of a pH, as well as harboring heavy metals, chlorine and other chemicals less than savory to your prize aquarium inhabitants. The answer to your water problems lies in owning your own reverse osmosis (RO) unit.
The Basics of Reverse Osmosis Units
RO units purify the water by forcing tap water through a series of membranes and filters. The membrane lets the water molecules move through, but larger molecules, such as limestone and other minerals, and contaminants are stopped by the membrane. The end result is water that is up to 99 percent pure, depending on the type of membrane used.
The most basic membrane is a cellulose tri-acetate (CTA) membrane, which is manufactured from organic materials. Using a CTA will purify your water from 88 to 94 percent, but this membrane does not remove chlorine from the water. You’ll still have to have a dechlorinator for your aquarium, or you can set your water out for 24 hours before using it in order to let the chlorine gas dissipate.
A more advanced membrane is the thin film composite (TFC) membrane. Made of synthetic material, the TFC membrane in your reverse osmosis unit will remove 97.5 to 99 percent of water impurities.
Another membrane consisting of synthetic material is the high removal membrane. Like the TFC membrane, the high removal membrane purifies your water from 97.5 to 99 percent, with the added benefit of also removing silicates.
Along with the membrane, the RO unit also comes with a carbon block, a sediment filter, and deionization (DI) resin, if it is a four stage unit. If the RO device you’re looking to buy has less than four stages, it means the DI stage was left out. The DI resin is another method of purifying your tap water by means of an ion exchange. An RO unit without a DI stage can purify your water to 98 percent. A DI stage added to your RO unit purifies your water up to 99.9 percent. Sometimes all you need is 98 percent pure liquid, but if your fish are really finicky, the extra 1.9 percent purity provided by the addition of a DI stage can mean a great deal to your aquarium success.
Maintenance of a Reverse Osmosis Unit
Once installed, the maintenance of a reverse osmosis unit is reasonably simple. If your tap water comes from a city municipal source and is loaded with chlorine, a good rule of thumb is to change out the carbon and sediment portions of the RO unit about every six months. The membrane in your unit often lasts for years. However, the membrane can clog with time or even develop holes. The best way to monitor your unit is with a total dissolved solids (TDS) meter, which lets you keep track of the quality of your RO operations. For example, the DI resin should read between 0 and 1 using a TDS meter. If the resin reads above 1, it should be replaced.
Reverse osmosis water is available by the gallon at supermarkets and aquarium stores. The point that makes owning your own RO unit worthwhile is that you control the quality of the water, since you can monitor your own unit. Purchasing water from the store means you have no idea when the RO unit last saw maintenance.