It is a basic truth of life on Planet Earth that clean, pure water is a priority for most all living things. This is particularly true for almost all fish and plants. When it comes to providing them with a proper environment, it is very possible the water that comes from the faucet in your home doesn’t have the right stuff for the inhabitants of your aquarium. It might even be toxic. The good news is, there is a rather simple solution: a Reverse Osmosis (RO) unit.

An RO unit can filter out up to 99 percent of the chemicals normally found in the water that comes from the tap by forcing it through a semi-permeable membrane. The semi-permeable reverse osmosis membrane only allows very small molecules (such as the water molecule H2O) to pass through it, effectively removing most water impurities including agricultural chemicals, arsenic , pesticides, and heavy metals, like lead and iron.

If you are a freshwater hobbyist, using an RO unit will result in water without both general and carbonate hardness, creating an environment where trace elements and electrolytes can be added to match the natural water conditions of our fish. It also allows you to use buffers to set the water’s pH wherever you wish.

For the saltwater hobbyist, an RO unit will remove a variety of chemical that likely could cause problems. Unfortunately, the standard reverse osmosis membrane does not remove nuisance chemicals like phosphate, nitrate, or silicates, all deemed undesirable because they contribute to algae growth (a big headache on its own!). So a Hi-S membrane, which is less permeable than standard RO membranes, will take care of the silicates, and adding a final-stage deionization (DI) cartridge handles the phosphates, resulting in the best possible water for your environment.

Maintaining your Reverse Osmosis unit is important

Regular maintenance of the RO unit requires replacement of the sediment pre-filter and carbon block. The manufacturer suggests replacing these cartridges after producing 1000 gallons of RO water. This is gauged by watching the pre-filter and noticing any color deviation from its original color. The semi-permeable membrane needs replacing after approximately three years. You can increase the life of the membrane by utilizing the optional RO flush kit.

So, now the question is, which RO unit is right for me and my aquarium setup? There are five simple questions you should ask when choosing an RO unit starting with what do I want to remove from my tap water? Does my water contain chlorine? Knowing the answer to these first two questions will help you answer the other three: How many filtration stages do I actually require? How many gallons per day (GPD) of purified water do I need? and What type of membrane do I need?

How much filtration do you need?

Ok, so, now let’s look at filtration. Various RO units feature a different number of filtration stages. Generally speaking, they vary from two-stage filtration to four-stage filtration, and depending on your needs, each accomplishes different levels of water purification.

A two-stage RO unit is generally light and compact, which makes it much easier for storage and transport. They contain a small inline pre-filter and the RO membrane. This is an excellent choice if space is limited, and is a good value at an economical price.

Three-stage RO units are larger, and employ carbon or sediment pre-filters to protect the delicate RO membranes. These are higher in quality, more durable, and thus are an excellent choice for regular use.

By adding deionization to the equation, the four-stage RO unit will remove the small amount of contaminants that remain, resulting in a purity level in excess of 99.9 percent, the highest level of water filtration you can get!

Overall, RO units definitely benefit your fish and plants by removing impurities in your water. Knowing how many impurities your water contains, helps you determine the best RO unit for your aquarium.