One fact is certain: the need to perform water changes is not universally endorsed. Some Authors, and several manufacturers, would like you to believe that if you use their products no water changes whatsoever are necessary. This sounds very appealing, of course, and hobbyists are eager to listen to such claims, and any similar ones that mitigate the need to actually perform "work" on the aquarium they keep.

In all my years in the freshwater and marine hobby, both as a beginner and as a more dedicated researcher in the last ten, I have never been able to convince myself that all forms of pollution that are present in the aquarium can be removed efficiently and thoroughly enough, simply by using the four prevalent methods of filtration: mechanical, biological, chemical, and fractionation, advocated in books etc.

Such filtration can do wonders for the water quality, especially nowadays with the appearance of more sophisticated equipment and trickle filters, but a number of compounds still exist that will accumulate over time in the water, because they are not being removed rapidly enough to prevent such a build up.

Water changes, using the right kind of water, of course, can achieve that result simply and very efficiently. All the hobbyist needs to do, is include such water changes in the routine maintenance practices that should exist for every reef tank. A chapter, later in this book, is dedicated to what such practices should include besides changing water.

It is most important that the right kind of water be used. Replacing water of lesser quality, with water that is of not much better quality does not make sense at all. Nevertheless, hobbyists do it all the time. Tap water, the most common source of replacement water, can be heavily polluted with nitrate, phosphate, chlorine, chloramine, phenol, silicic acids, pesticides, fertilizers, ammonia, etc. Tap water should, therefore, never be used in its raw state. It should be checked for all such parameters first. Additionally, tap water should be treated, chemically filtered that is, before salt is added, especially since hobbyists cannot check for many of the compounds that chemical filters can remove efficiently.

The recommended treatment consists of running raw tap water first through a good quality activated carbon (one that does not add phosphates and heavy metals to the water, and many do), and then through another chemical filter to polish it even further and remove any traces of pesticides, phenols, amines, copper, zinc, and many other undesirable compounds. The medium suggested to achieve this is the Poly Filter (from Poly Bio Marine Inc., or their molecular absorption discs which provide even stronger chemical filtration. Flow water through both very slowly. No more than 30 to 45 gallons per hour, to ensure a long contact time. Water that has been treated in such a way is of excellent quality and can safely be used.

Of course, you must also pay attention to the quality of the salt that you are using. It should not contain phosphates and nitrates, and should be free of impurities. The smaller the amount of residue remains after the salt has dissolved, the less impurities it contained, more than likely, to begin with. Such would, obviously, be a sign that the salt you are using is of excellent quality.

As already stated several times, if you are using activated carbon, you must ensure that it is of superior quality. We have already discussed this elsewhere in The Marine Fish and Invert Reef Aquarium book however, it is important enough a matter for me to repeat it once more. Many carbons sold in the hobby will leach phosphates back into the water in your tank, and pollute the tank in the process. Excess phosphates, defined here as more than 0.1 ppm, yes, one tenth of one part per million, will soon give rise to micro-algae outbreaks, and will result in a very unsightly looking aquarium. Such algae will be difficult to deal with as they are hard to remove once they appear in the tank.

Having said all his, how much water should you change? There is no real scientific literature to back up the recommendation that I have made for a long time, which is to change about 4 to 5 percent per week, or better even, 2 percent every 2 days; but I have, over the years, had excellent results whenever I was doing so.

What could happen to your tank and corals if you do not perform such water changes? Probably nothing for a while, but as time goes on, you may find it difficult to keep certain types of animals alive, or they may just not look as good as they used to. This due to the already mentioned accumulation of noxious compounds. Often hobbyists run aquariums that look really good for months in a row, all types of corals and invertebrates do just fine, and thrive. Suddenly, for no apparent reason the hobbyist, however, senses that something is wrong. Things are not the way they usually are.

The difference may not be apparent to others, but it sure is to the hobbyist who knows his or her own tank. Something is wrong, you know it, you sense it, but you can't define it. The tank does not look as vibrant as it usually does. Your sixth sense tells you that something is not the way it normally is. It tells you that something that you cannot define is happening.

Has it occurred to you that this "malaise", so to speak, has to do with water quality, and that the progressive increase of certain compounds, noxious ones, perhaps from traces in the beginning, to parts per billion after a few months, is a possible cause for this undefined trouble, and is affecting the well being of the animals kept in the aquarium.

Because certain animals are more sensitive to certain types of compounds than others are, this malaise may manifest itself in several ways. Frequently the hobbyist will observe that he, or she, can keep anything in the aquarium, except for instance carpet anemones, or certain types of Tangs, or Flame angels, etc. The reason such animals do not make it in a tank has nothing to do with the hobbyist. It has to do with the water quality. Pure and simple. Water changes are therefore very necessary! Perform them regularly and improve the overall quality of your tank's water.

Another indication of trouble may be the fact that corals that used to open up and stretch to the point of what looked like "bursting" suddenly no longer do. Their general appearance can still be considered acceptable, but it certainly is not as magnificent as it used to be. Again, such is due to a deterioration of the water quality. Do something about it, change water regularly and eliminate the build up of noxious compounds as a possible cause of problems in your tank. If you change water regularly it does not become a chore, and when you only have to change a little at a time the task becomes easier, faster, and you are less likely to spill water. Because it is an easier task, you are also more likely to actually make the water changes. The easier the task, the more likely you are to perform it regularly.

Four to five percent a week, or 2 percent every 2 days is an average that I have been satisfied with. Every tank is a different ecosystem and may require some degree of adjustment. You may find that your tank does better with a slightly larger water change, for instance 5 or 6 percent a week, or as some hobbyists report 10 percent a week. The ultimate amount is up to you to determine, but changing some amount of water you must.

Keep in mind that it is most important to prepare the water that you will use to effect water changes in advance. Do not prepare it minutes before you plan to use it. Such water is too rough, too aggressive, too crude, and will stress the fish and other tank inhabitants. Prepare the water at least 24 to 36 hours beforehand, aerate it, and bring it to the right temperature and pH. This all ensures a greater stability of the water chemistry, and reduces strain on the filters and on the tank lifeforms. Less stress means healthier looking animals and a better looking tank.

It is a good idea, in fact, to have some spare prepared salt water ready at all times, as the need for such water will arise from time to time when it is least expected. If you have a few gallons of standby water, you will not have to use freshly prepared one that is not as safe to use. Aged water is definitely better. This is especially so if the need for spare water is created by some other emergency that may already have caused stress. Don't intensify the existing stress. Have some water ready.

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