One of the questions most often asked by one new to the hobby is can I use Tap Water or do I need to get a RO/DI unit? Well the answer is yes more times than not. Trouble is you just may not want to due to the sensitivity of reef tanks. I will explain some of the short comings of Tap Water –VS- RO/DI.

There are several problems that can arise when using Tap Water in a reef tank. Tap Water is usually derived from Lakes or under ground Aquifers. Most of this water is run off from rains or seeps slowly into the ground replenishing lakes and aquifers. In this process water can pick up a lot of things such as phosphates from fertilized crop lands. It can also pick up a number of other elements such as Silica, Iron, Sulfur as well as Organic Material just to name a few.

Additionally although PVC pipes are taking a strong hold in the world of plumbing, Iron and Copper pipes are still used extensively. Water passing through these types of pipes, will invariably contain Iron, Copper and Lead that is often used to connect the pipes as the pipes are slowly worn away by oxidation and the flow of water.

While these all seem to be no big deal, in a saltwater tank these can often cause the aquarist many problems. Copper, Lead, and Aluminum can be quiet toxic in small concentrations in the reef tank. Elements such as Iron, Phosphates and Silica can often provide the fuel necessary to spur uncontrollable algae blooms in the reef tank. Additionally Tap Water will often contain Ammonia, Nitrites and Nitrates, all three of which reefers go to great lengths to minimize in the tank. Water Treatment Facilities often times add additional chemicals to the water. Things such as Chlorine, which must be neutralized before use in the tank as well. This can often make Tap Water unfeasible for use in a reef tank.

As such many Reefers use a RO/DI unit that filters out all of these contaminates making the water far more suitable for use by aquarist. These units can indeed though be somewhat expensive to buy and almost as expensive to maintain as they will require filter changes on a regular basis. Without going into a long and drawn out explanation these filters are able to remove 99.9% of these contaminates. Hence the reason these units are the “darling” of many serious hobbyist.

Not every Hobbyist has the money available to invest in such specialized gear, or lack the room for such a set up. Lucky for us, depending on the quality of our tap water, it can often times be suitable despite. Much of the water used by Municipalities often have very low levels of these contaminates and after being de-chlorinated can often times be quiet adequate for use in a reef tank. This however will depend upon the water in question. To find out what your water contains you can often contact the Public Utility company and get a print out on the water analysis in the area being used. This can provide you with the necessary information needed to determine its suitability. There are a number of products on the market that can be used in the reef tank that will absorb these things, such as Phosphate Sponges, Resins etc…Some of these products can be quiet expensive to use though. Refugium’s can be used to good effect if installed on a reef tanks filtration system to remove Nitrates and organic nutrients as well.

So check your Tap Water out today. You might be surprised at just how well it can stack up, and that you just might not really need that expensive RO/DI unit after all!

Good luck and Happy Reefing!