Continued from page 8

8.13.5 TANGENTIAL FLOW FILTRATION:

Yet another form of filtration, closely related to reverse osmosis, but not presently used in the hobby, is tangential flow. Water is flowed through a cartridge under over-pressure. The housing in which the cartridge is placed allows the water to escape either by going through the

cartridge, or by escaping through a smaller diameter hole than the input one, untreated, to rejoin the mainstream of the water.

The treated water will be much purer as a result of having passed through a cartridge that is designed to remove certain compounds. Typically, these cartridges can remove nitrate and phosphates and a number of other compounds as well. The more they remove the more expensive they become. Unfortunately, at this point in time, all cartridges are much too expensive for use in the hobby, fetching well over $125.00 as a minimum, and all require frequent replacement. Perhaps, as time goes on, cartridges that are priced more at the hobby level will become available.

8.14 USING ACTIVATED CARBON IN THE SYSTEM:

Activated Carbon can be used to pretreat the water, as already discussed in 8.13.4. If is often used as well in the main system, to treat the tank water continuously.

Because of the many problems associated with the types of activated carbon available in the hobby, even under very fancy names, the hobbyist must pay careful attention to the brand he buys, and test it to ensure that no phosphate or heavy metals are leaching from the carbon into the tank's water.

Good quality carbon must be used in all systems that rely on ozonization, and reef systems should. All water exiting a skimmer, or reactor, in which ozone is injected should first be flowed over activated carbon and then be remixed with the main water. Such will remove residual ozone and prevent any from ending up in the tank and possibly damaging the corals and invertebrates.

A.C. is a form of chemical filtration, and we have already seen that some form of chemical filtration is a must on a reef tank. Use activated carbon and/or Poly Filters but make sure that the water to be treated flows freely through the carbon and the pads or discs.

Do not use large amounts. Such is not necessary if you follow my recommendation to use Poly Filters and/or molecular absorption discs. This is unlike what I have recommended in previous printings of this book. If you decide not to use Poly Filters, you must use more activated carbon, and you must test your tank water from time to time to determine whether or not your carbon is still detoxifying the water. This is done by using a small piece of plastic on which a few faint yellow marks have been made. Submerse the plastic in the tank, and look at it from a distance. If you can no longer see the faint yellow lines, you must change your activated carbon immediately as it is no longer effective since yellowing matter (Gilvin, Gelbstoff, Yellowing matter) is present in the tank.

How much carbon should you use? If Poly Filters or discs are also placed in the system, a maximum of 1 pint to 1.5 pints per 50 gallons of water is enough. If you do not use the Poly Filters, place 3 to 3.5 pints per 50 gallon in the filtration, making sure that water flows through the carbon easily and continuously. So-called carbon bags are not always the best solution, as often water has a tendency to flow over them, rather than through them. If the water does not flow through the bag it is not in contact with the activated carbon, and you are not using the activated carbon efficiently.

8.15 LABORATORY WATER TESTS:

A time may come when, after you have tested your water extensively and find nothing wrong using all tests that are available in the hobby, the animals in your tank are not opening, are dying, or just do not look good. All water quality parameters test out well within acceptable ranges, your redox is high and your dissolved oxygen levels are good. There does not seem to be a logical explanation for what your tank is going through, but you know there is a problem, even though you have followed all my recommendations and adhere to a strict husbandry program.

Such may be the time to consider using a water testing service, and have a real thorough analysis done to determine whether some compounds are present in the water that are harming the corals, invertebrates and so on. Usually a "drinking water analysis" will tell you enough about your water, to allow you to make a determination as to what the problem may be. Such a complete water quality test is not inexpensive, so make sure you really need to have one done before going ahead with it. Since the results of such an analysis are given to you with both the acceptable levels, and the ones in your water, their interpretation is rather easy, and abnormalities will be obvious.

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