Reverse Osmosis for the Saltwater Tank
The key to cultivating a healthy saltwater tank is to start with a good foundation – the water you use to fill your tank will have a significant impact on the water quality in your tank. If you use regular tap water to mix the saltwater for your aquarium, you may find that it does not meet the parameters your tank inhabitants require. Certain species of fish and saltwater invertebrates have specific requirements for pH and water hardness – if your tap water does not naturally fit the requirements for these species, you may have to go through a great deal of effort to change your tap water. Rather than going through this hassle every time you perform a water change or clean your tank, think about investing in reverse osmosis unit. Read more to learn what a reverse osmosis unit is and how it could benefit you and the inhabitants of your saltwater or reef tank.
What is Reverse Osmosis?
Reverse osmosis (RO) is simply a type of water purification process that involves forcing water through a semi-permeable membrane to remove impurities. The reverse osmosis process typically removes 90 to 99% of tap water impurities, leaving the water free of minerals and a variety of other contaminants. The efficacy of the RO unit in removing impurities largely depends on the type of membrane the unit uses – cellulose tri-acetate (CTA) membranes are only 88 to 94% effective while Hi-S membranes have a removal rate between 97.5% and 99% and they were also particularly useful in removing silicates. If you have done some research on keeping a saltwater tank you may be familiar with deionization (DI) as an alternative method of purifying tap water. Both of these processes serve to remove impurities, they just use different methods – deionization involves the principle of ion exchange, replacing impurities with pure water. Some saltwater aquarium hobbyists choose to use both an RO and a deionization unit to ensure that their tank water is 99.9% pure. In many cases you can buy combined RO/DI units or you can buy an add-on DI unit that can be attached to a RO unit.
Benefits of Reverse Osmosis
In addition to purifying your tap water, one of the main benefits of a reverse osmosis unit is that it is very easy to use. Once you install the unit, very little maintenance is required – you should only need to flush it out once in a while and replace the pre-filter every six months or so. The membrane, however, should last for several years. Another benefit of using reverse osmosis to treat your tap water is that you will have fewer problems with excess algae in your tank. In removing impurities from your tap water, the process of reverse osmosis also removes some of the nutrients algae need to survive which will result in fewer problems with algae growth. Less algae and fewer impurities will also lead to cleaner tank water and higher water quality – all of these things add up to a healthier environment for fish and other tank inhabitants.
Choosing an RO Unit
When choosing a reverse osmosis unit one of the first things you must determine is the number of filtration stages you want – RO units are available with 2-, 3- and 4-stage filtration. RO units offering 2-stage filtration are fairly small and compact – they are reasonably priced and good for tanks that do not offer a great deal of space. 3-stage RO units typically contain one or more carbon or sediment pre-filters and they tend to last longer than the smaller 2-stage RO units. The third options, 4-stage RO units, also include a deionization feature which leaves the tank water 99.9% pure. In addition to selecting the number of filtration stages you also need to think about the type of membrane you prefer and the capacity of the unit itself.
Tips and Considerations
If you aren’t ready to make the commitment in purchasing your own reverse osmosis unit you could start out by purchasing pre-mixed RO water for your marine tank. Most aquarium supply stores and large pet store chains sell pure RO water or pre-mixed salt water. While this option may seem pricey compared to mixing your own water, it may be a cheaper alternative to buying your own RO unit. If your tap water needs to be altered to meet the requirements of your tank inhabitants, purchasing RO water may also be less expensive and less hassle than what you would need to do to modify your tap water. Before you make a decision either way, take the time to calculate approximately how much RO water you would need on a monthly basis given your tank volume and the frequency of water changes to determine which option is more cost effective for you. If you have several friends who also keep marine aquariums, you might consider seeing if they would be interested in sharing the cost of the unit with you so they too can use RO water in their aquariums.
A reverse osmosis unit is an excellent piece of equipment to have and some would argue that it is a necessity for a thriving marine tank. Before you go out and purchase an RO unit, however, you should take the time to learn the basics about this type of equipment and determine which type of unit might be best for you and for your tank.