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8.13 WATER PRETREATMENT:
8.13.1 INTRODUCTION:
The water chemistry in the tank is dependent not only on the amount of pollution that is generated continuously in the aquarium but also, and to a great extent, on the amount of pollution that is introduced into the tank because it is part of the water used to perform water changes and top-offs. We have already touched on this earlier in the book, and it is important for you to remember.
Although, technically speaking, not a test in itself, the values of all tests performed later on the tank's water can be greatly influenced by the quality of the water that you use to fill the tank, and so on, because such water may contain a number of compounds that are not acceptable for reef tank water, and that will result in much higher readings when you test the tank.
With that in mind, pretreating the water that you use, not only makes a lot of sense, but becomes a requirement in many areas of the country where tap and well water are of such inferior quality that they must be purified before they can safely be used on the reef aquarium.
Well water may contain leachings from nearby fields, traces or more of phosphate and nitrate based fertilizers, PCB's, VOC's, pesticides, insecticides, and so on. Often these are present only in very small quantities, in the ppb range (parts per billion), but over time such ppb levels will build up to levels that become toxic, if not removed in some form or another.
Pretreating the water also gives you the peace of mind that you need not suspect the water source when anything happens in the tank. For example: you determine during a routine test that your phosphate levels are 0.15 ppm. Obviously because this is about 3 times higher than it should really be, you must determine the reason. Since you always pretreat the water that you use, and have tested the salt, you know that the cause lies elsewhere. Perhaps overfeeding, overcrowding, another type of activated carbon you obtained, etc. are the cause.
In the long run, treating water yourself is much less expensive than buying distilled or deionized water from an outside source, at anywhere from $0.60 to $0.99 a gallon. This may not seem a lot on a per gallon basis, but for hobbyists maintaining a 55 gallon tank, who perform 5 percent water changes a week, and need another two gallons a week for top-offs, this can work out to $15.50 a month, or $186.00 a year. A similar calculation for a 70 gallon tanks yields respectively $22.00 and $264.00. Taking a closer look at such numbers quickly convinces hobbyists that it is far cheaper to buy a small water treatment system and prepare their own water.
Consider too that when you have your own installation you do not have to lug bottles of water around, and that it is "always" available, even on weekends, or on holidays, when the shops you get water from may be closed, or may have run out.
Last but not least, whatever installation you buy will serve more than just one purpose. Such systems make excellent drinking and ice water for yourself. Everything prepared with it tastes better too.
8.13.2 REVERSE OSMOSIS FILTERS:
Reverse osmosis filtration is one way to remove nitrates, phosphates, sulfates, silicates and many organic impurities from the water, including pesticides and so on. R.O. systems can be extremely efficient at removing impurities if you buy the correct type of unit. Many types are offered for sale but not all are suitable for use around the reef tank. Depending on the type of membrane used the efficiency of the unit will vary, and so will the price.
The better reverse osmosis filters use thin film membranes and give efficiency rates of over 99 percent, not 90-95 percent as several units we tested do. Efficient reverse osmosis units cost more money because the components that must be used to increase the efficiency to the 99% level greatly increase their production cost; indeed, the increase in efficiency from an average of 95% removal to 99% removal requires the use of much more expensive materials.
If what you are interested in is truly removing all impurities from the water - and that is the type of unit you should be looking at buying - you must buy a unit that includes the following three forms of filtration:
When buying such a unit ensure that you can service each of the above parts separately and easily. The micron cartridge will have to be replaced every couple of weeks, the frequency will depend on how much particulate comes in with your tap or well water; the carbon filter may need changing every two to three months, especially in areas where strong chlorination is the norm; the reverse osmosis membrane is probably not in need of service for up to 12-15 months or even more, depending on the quality of the water in your area.
Keep the following in mind when using a reverse osmosis system:
The effluent from reverse osmosis filters, especially from the three part filters just mentioned, is of very high quality. It can be used immediately, or can be stored and aerated. If you aerate it, filter the air going in to the water through activated carbon first.
The advantages of reverse osmosis are many:
The only disadvantage that I need to point out is that reverse osmosis wastes a lot of water. This may be a problem in areas where drought or water restrictions are common.
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