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Photo by: jon hanson

One of the many lesson’s I’ve learned since starting my 75 gallon saltwater tank is the importance of water quality. In a freshwater tank, you can use normal tap water straight from your sink that has been dechlorinated. This is not the case for saltwater tanks. Saltwater requires excellent, high quality, and pure water. Available water sources include:

• Tap Water
• Well Water
• Distilled Water
• Filtered Water
• Ocean Water
• Premade Saltwater
• RO/DI Water (Reverse Osmosis/De-Ionized Water)

Tap water

Use of tap water in saltwater tanks has been linked to health issues with fish, problems with invertebrates and most notably the primary source of algae problems. Tap water, while safe for us to drink, is full of harmful impurities including Fluoride, Chlorine, Chloramines, Nitrates, Phosphates, and even metals (like Copper which is lethal to invertebrates). None of these impurities can be added to your saltwater tank without causing harm.

If you decide to use tap water, it’s critical that a water conditioning product be used. There are many good and effective products on the market. One I’ve personally used with success is Kordon Aquarium NovAqua Plus Water Conditioner

Well water

Well water is similar to tap water and doesn’t eliminate the concerns. Wall water can even introduce additional metals, parasites, bacteria, pesticides, and radon. An additional concern that should be considered with well water is high alkalinity. Of course none of these things are good for your saltwater aquarium or it’s inhabitants.

Distilled water

Distilled water is generally fairly pure. One area of concern I’ve come across in my research is that distilled water is sometimes stored in copper tanks. Given the issue of copper and invertebrates, be aware that using distilled water can possibly introduce copper into your tank.

Distilled water is also fairly expensive and can quickly become cost prohibitive for a large tank. My personal thoughts on the use of distilled water should be to use it only when you don’t have any other better option.

Filtered water

Many home owners have installed carbon based water filters on their kitchen sinks and sometimes even the water supply to their homes. While these filters remove chlorine and improve the taste of the water, they don’t generally remove harmful metals, phosphates, nitrates, etc. These filters are designed to improve water taste, not improve overall water quality.

Use of carbon filtered water is only marginally better than tap water and not an option I would recommend for your tank.

Ocean Water

While this would seem like a good option, it generally isn’t. Sea water contains lots of living organisms. Many of them will not survive in an aquarium and die off, resulting in pollution of your tank. Additionally, water that is close to shore isn’t suitable for use in aquariums due to pollution and high levels of bacteria and other contaminants. Suitable water for an aquarium use can only be retrieved by going a few miles out. Even then the water must be heavily filtered and properly prepared.

Pre-made Saltwater

Most stores that carry saltwater aquariums now carry pre-mixed and ready to go saltwater. A number of more specialized fish stores also mix their own saltwater and make it available for sale to customers. Using this option is by far the easiest but not the most cost effective. Also for a large tank, carrying that water to your home can be quit cumbersome.

RO/DI Water

In my opinion, this is the best option. RO/DI water is 98-99% pure. RO/DI is created through the use of a RO/DI filter that is a highly efficient means of producing pure, clean water. RO/DI water can be purchased from your local fish store, but a more cost effective way and safer way to produce it is by purchasing your own filter. Filter prices range anywhere from $60.00 to hundreds of dollars depending on features and quality.

Due to limited finances, I purchased a 100GPD unit on eBay for $61.99 and so far have been very happy with it. Even better units are available at Melev’s Reef, The Filter Guys and from Air, Water, & Ice.

Financially, over time purchasing an RO/DI filter is the best option. By the time you factor in the water you are purchasing, the chemicals you might need to buy, and factor in gas back and forth from the store, the RO/DI filter will quickly pay for itself.