How Important is Water Quality in a Reef Tank?

By Robert M. Metelsky
Author of the book Simplified Reefkeeping, 3rd ed. available at simplifiedreefkeeping.com
Aquarticles

Nothing will insure your success as much as the quality of your water! One of the most important elements of an enclosed reef system is the water. With human beings, clean fresh air is necessary for good health; in a reef tank, the water is the vital component.

The water you use will have the greatest effect on the success or failure of your reef tank Do not make the mistake of assuming your tap water is suitable. Most likely it is not. Many a novice reef aquarist has paid dearly for overlooking the composition of plain tap water.

USING PLAIN TAP WATER

The first approach is to try to use your tap water, just as it comes out of the faucet. This seems like the easiest way, but it has the most potential problems. If you insist on using your tap water, I would strongly suggest that you have it tested in a laboratory. You will find such laboratories listed in the Yellow Pages. The tests cost about $10 each. You want the lab to test for phosphate and silicate (algae producers), nitrate, lead, and copper. So you need five tests @ $10, which is $50. Even if the readings are low, you cannot be absolutely sure the water won’t cause problems at some point. However, you may get extremely lucky and be able to use your tap water.

Average tap water will usually induce micro-algae.  If you take this approach, there will be only one way to know whether it is satisfactory: once you have the tank set up and you have done the initial cycling process, if you don’t have a persistent algae problem and your livestock seems to be thriving, then you may assume the water is okay. I would not recommend this approach, as you may risk stressing or even killing the delicate and valuable specimens you have purchased. This may seem like the easiest and cheapest way to go, but I have found out that it is not.

The best approach is to use purified tap water. I have found this has been the most convenient, least expensive method to get top-quality water when and where you need it. This is a primary requirement of the reef.

What You Will Need

  1 carbon prefilter, single stage (plumbing supply house)
  1 carbon filter, dual stage
  1 reverse osmosis or deionizer

Keep in mind that you cannot afford to cut corners in this area of your system. As stated from the beginning, nothing will ensure your success as much as the quality of your water.

Let me describe my system. First, it is necessary to have a cold water supply from your home, preferably near by the tank. In my set-up, the tank is about 8 feet from a sink. I purchased a 3-way tap to tie into the cold water pipe, connected a piece of 1/2” plastic water pipe, and ran that next to the tank with a plastic garden hose type spigot.

Having a water supply at the tank is convenient and practical.  Now I have a water supply right at the tank, with a shutoff, which is ideal. This is extremely helpful when you do water changes and when adding the make-up water, which will be done frequently. I prefer not to have to wrestle with messy and inconvenient buckets and containers full of water.

To the male spigot I connect a length of garden hose, approximately 36”, with a female end to it. This is connected in series to a single-stage carbon prefilter, then to a dual-stage carbon filter, and finally to a deionizer, which has a 36” length of vinyl tubing for the outlet. The result is pure triple-carbon-filtered, deionized water. My make-up water system is located on the side of the tank, where I mix the water for bimonthly water changes and the make-up water for evaporation.

A Reverse Osmosis Unit:

The advantage:

It supposedly produces a higher quality water.

The disadvantages:

It processes water slowly.
It must be near a drain for the waste water.
The water supply from the house has to be on for extended periods of time.
The unit may have to be left unattended while it is on.
It will need a certain water pressure to operate properly. City water is usually okay, but a well pump may
provide insufficient pressure. (Check the manufacturer’s recommendation for water pressure.)
The water may have to be transferred from a large holding container to the make-up mixing system near the tank.
There are more fittings on the unit that could malfunction (strip if over-tightened, need replacing) or leak at some point.

A Deionizer:

The deionizer is a much simpler design than the R.O. unit. It operates on a one-stage principle, using a container filled with a resin material that removes contaminants. I find that the quality of water it produces is perfectly acceptable for my reef.

The advantages:

A ready supply of water. A deionizer can produce 5 gallons in 1/2 hour.
There is no bypass waste water, so no need for a drain.
It can be set up right near the tank and make-up system, if there is a water supply nearby.
It does not have to be left on for extended periods unattended.
It has fewer fittings than an R.O. unit (fewer opportunities for something to malfunction).
It is easy to service.

The disadvantage:
It is considered by some to produce a lesser quality of water than reverse osmosis.

When selecting purifying resin for the deionizer, try to get the “indicating” type. This resin will change color when it needs to be replaced. This can help you avoid replacing it prematurely, or waiting too long past the life span of the resin’s contaminant-removing properties.

Water purification products are rated by the amount of water they will process in a certain period of time. Determine how much water you will be using for set-up, bi-monthly water changes, and evaporation replacement. Compare the rating versus the price. Then purchase equipment that is slightly larger than you absolutely need. If you have a good relationship with your retailer, and his prices are competitive, purchase from him. Usually, he will stand behind the product he sells, and have the parts and resin when you need them.

Prefiltering the R.O. or deionized water

$$—Extend the life of the resin—$$

Prefiltering the tap water is extremely beneficial and economical! Placing one or more quality carbon filters before the water enters the R.O. or deionizer will remove many harmful contaminants and impurities before the water goes into the expensive stage of purification. This will extend the life of the resin, which is costly. A quality carbon water filter is relatively inexpensive. A large, two-cartridge, carbon, home water filter is about $60. The replacement cartridges are about $12 each, and they will last 6 months easily. Small versions designed for the home can be purchased for less.

My set-up has a small single-cartridge unit connected to a larger double-cartridge unit, which then runs into the deionizer. My thought is that the first (single) unit is used as a prefilter, and ideally traps the bulk of impurities and sediments. This initial single cartridge is replaced every 2 months. The second, double-cartridge carbon prefilter handles what the first has missed, and is replaced at 4-month intervals. The final deionizer resin lasts approximately 5 to 6 months. I use 70 gallons a month for water changes and approximately 20 gallons to replace evaporation; this makes a total of 90 gallons a month, or 1,080 gallons a year.