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Treating Water Before it is Used
Mechanically
Mechanical filters are meant to remove dirt, detritus, particu- late matter, debris, etc. from the water before it is being treated further. You are familiar with mechanical filters, because you already use them on the tank itself. They are often referred to as fine filters or pre-filters.
A canister filled tightly with filter floss, or some similar material will do the trick for rough type impurities. If you want to filter down to the smaller material you will have to resort to the use of filter cartridges.
Such cartridges do a fine job, but the cost of using them can creep up on you quickly. You are probably acquainted with "micron" filters, rated in values such as 100, 75, 50, 25, 10, 5, 1 and some even less than one micron. Keep the following in mind when selecting a micron cartridge of any type of rating : there are two types, referred to as "nominal" and "absolute".
Absolute means the cartridge does not let any material larger than the rating through, nominal lets some through. For example, a 50 micron nominal cartridge will let some 60, 70, etc. material through; an absolute 50 micron cartridge will not. Absolute rated cartridges are quite more expensive than nominal ones . If you plan on using this type of mechanical filtration, stick with nominal rated cartridges.
One advantage of using "very small particulate" filters, is that they remove not only debris, but also parasites, bacteria etc. To do so, however, you will need to use special sub-micron filters (<than 1 micron). This is also called cold sterilizing.
The smaller the rating of the cartridges, the faster they will clog up, unless you place several of them in series, starting with the highest. A series of 100, then 50, then 25, then 10, then 5, will give excellent results, but is much too expensive to set up for our purposes, especially in a "basic" Reef.
Whether or not you need to pre-filter, or fine filter the water you will be using,often depends on the source of the water itself. Tap water and well water, will contain few "visible" particles, but keep in mind that even with good eye sight, you will not see debris smaller than 40-50 microns.
Certain areas of the country have water that contains consider- able amounts of debris, of all forms, and it is recommended to pre-filter the water if such is your case. If you buy a filter assembly to do so in a do-it-yourself type store, look for "rust and debris" canister filters. They usually cost between 30.00 and 40.00 dollars, and replacement cartridges can be bought for around 5.00.
Anyone with well water should pre-filter as well, especially because of usually high amounts of undissolved mineral and other compounds it contains. Use the same filter type as if you were removing rust and debris from tap water.
Plain sand filters will remove a fair amount of debris as well, and are easy to set up. All you need is an old aquarium, some sand and flexible hose. The diagram below shows exactly how to set such a filter up.
Sand Filter for Fine Filtration
A simpler system yet, would be to use two buckets, one sitting on top of the second one. The first one has a perforated bottom over which plastic screening material is laid. This is then covered with sand, or filter floss, or foam, or some other material that allows fine filter- ing. The water goes through the material in the first bucket and drips, respectively flows, into the second one, cleaner and mechanically filtered. This is, for sure, the least expensive way to set up a mechanical filter, but it is not to be considered a low micron filter. It will remove gross impurities, and some finer as well, especially if you use a thick layer of fine sand.
Remember to rinse the sand after each session. Let it dry in a flat tray to prevent the formation of anaerobics. If you do not let it dry, rinse it each time before you use it. This is simpler, and is probably what most Hobbyists will do.
These filters can be made more efficient by flowing the water through layers of progressively finer, and finer, filtering material. The coarser layers remove the larger material, and the progressively smaller ones are removed as the water has to go through smaller (finer) filtering media. Both Moe (1982) and Spotte (1976) give more details on such filters.
Remark : fine filters such as these do not remove dissolved material, e.g. phosphates and nitrates. To do this you will need a totally different filter, described later in this section.
The example uses different mesh sizes of gravel and sand, to go from very coarse to very fine. Between uses, the filter should be allowed to drain. Before collecting water for use in the tank, the system should be run for a few minutes to remove any possible anaerobic contamination. If you wish, you can place filter floss between each layer to keep them separated, although that is not really necessary.
Moe (1989) states that chemical filtration, of which activated carbon is but one example, is in fact mechanical filtration on a molecular basis. Chemical filters, indeed, remove "dissolved" material at the molecular level. The chemical filters described earlier, remove "undissolved" material.
A.C., or activated carbon has been around in the hobby for a long time. Unfortunately my experience with such A.C. is not good at all, except for a few brands that use the better quality material, especially the more expensive varieties.
Plan on using the latter if you include A.C. filtration in your pre-use treatment of the water. Don't waste your money on a product that may add more undesirable matter to the water, than there already is. One such compound frequently added is "phosphate" in many forms. Phosphate is the cause of many problems in the tank, and leads to the appearance of micro-algae, often in uncontrollable quantities, that can quickly "ruin" an otherwise fine looking aquarium. These low quality carbons (some not even activated) should be avoided at all cost. Foreign imports too, should be tested before use in the tank, as I have had several bad experiences with 2 types, and have lost corals as a result.
What determines the quality of the carbon, is the source of the base material to make it, and the fabrication process used. This gives rise to the existence of the following main types of activated carbon:
- charcoal
- bituminous carbon
- lignite carbon
- coconut shell carbon (sometimes called vegetable base)
- mixtures of the above, or "non-descript" origins of carbon material, e. g. bone, some woods, and others.
Any type of carbon can provide excellent results in certain specific applications. This is also the reason why every manufacturer can claim that their carbon is just "the" best. It turns out, however, that in aquarium use "the" best for another application, may not be adequate for what we are trying to do, keeping a vibrant looking reef tank.
Many carbons leach phosphate into the water, a fact first point- ed out to me by Ken Howery, and further confirmed by personal testing, and the results of tests made by readers of Marine Reef, the newsletter published by Aardvark Press.
Because phosphates are at the source of many micro-algae problems in Reef and other tanks, we must at all cost avoid adding more phosphate to the water. In fact, we should do all possible to remove PO4 through whatever means we can.
Ortho-Phosphate, organic phosphate, nitrate, ammonia, nitrite, phenol, volatile organic compounds, amines, and many other chemicals that are undesirable can be present in incoming water, whether it be tap, or well. Additionally, tap water can often contain high amounts of chlorine, and sometimes chloramine and hexametaphosphate as well. All of the latter need to be removed, before that water can safely be used and added to the reef tank (and fish-only tanks as well of course).
Activated carbon of good quality will remove most of the above compounds (there are better methods as we shall see a little later) and neutralizes chlorine as well. It should, therefore, be considered in a set up to pre-treat tap and well water, and not overlooked completely. There are excellent carbons available.
For a much more in depth explanation on the differences between the various forms of chemical filtration, e.g. ion exchange, adsorption, absorption, molecular sieves, reverse osmosis, tangential flow filters, and so on, read Moe (1989) The Marine Aquarium Reference, published by Green Turtle Press, a book all Reef Keeping Hobbyists should have, and read.
Based on what we have seen so far, a filter to pre-treat the water could look as follows (there are many variations) :
The 2 component unit shown can be improved upon by using a can- ister that can be set up with both carbon, and diatomaceous earth. Such a canister will remove whatever A.C. removes, and will filter down to very low micron levels. Unfortunately my experiences with diatomaceous earth filters do not let me recommend this set-up. You could however consider a System 1* micron filter set-up, with powdered activated carbon.
Fill here
Pump
The above system pulls water from the vat or old aquarium, circulates it through a first and then a second canister, and then back to the vat. Water from a well or tap is used to fill the vat. The system, once switched on, can recirculate without the Hobbyist having to stand around. Fill one canister with a good quality activated carbon, and the second one with sand, or floss, or a similar mechanical filtration medium. This simple system will give you better quality water than you would have if you did not treat at all, but can still be improved upon as we shall see in this chapter.
Such filters are advertised in the magazines you read, and are worth looking in to, as they allow you to combine two filtration steps in one unit. When you now supplement this with the next one that we recommend, you will then have a complete pre-filtration system that cleans the water more than adequately for use in your Reef aquarium. Activated carbon is also used in the system's filtration, especially to control residual ozone. See previous chapters for more details.
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