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Molecular Absorption Filters :
My favorite form of filtration, because it removes more from the water than activated carbon does, can be visually inspected easily, does not leach anything back into the water, and is cost efficient to boot.
Molecular absorption filters come in pad form, or in discs, and are manufactured, and sold,by the Poly-Bio-Marine Company through dist- ributors only. There are, however, so many of them that you should not have any problems finding "Poly Filters" or discs in your area. If you have not tried them yet, you definitely should.
I recommended already that you use them in your actual system filtration . Now I would like you to make them part of your pre-filtration stage as well. This is the last component of an efficient filtration set-up.
The set up I recommend for treating water before using it for your tank thus comprises three parts :
- activated carbon for chlorine removal and some impurities
- fine filtration for removing particulate matter
- molecular absorption for final polishing of the water.
The effluent from such a system is just as good as what you would obtain from systems costing perhaps 5 to 6 times more, at least. Don't waste your money. In the type of tank we are concerned with in this book, you must use every dollar you are going to spend as wisely as possible, so you can include all the equipment that is recommended for a minimum set-up.
Because Poly Filters and discs change color as they progressively exhaust their absorption capability, it is easy to determine when they need to be replaced. For pre-filtration purposes, they should last quite some time. Many more months probably, if the water in your area is not of all that bad quality to begin with.
Although often seen advertised in Hobby magazines, and indeed an efficient way of purifying the water, I see reverse osmosis on the small tank as overkill, insomuch as the type of R.O. unit you require to do a good job, is expensive, and still the units are slow.
In addition, reverse osmosis filters waste a lot of water. At best,for every gallon of filtered water you end up with, you have, cons- ervatively, wasted another four (more likely 6 or 7). Reverse osmosis filters are very slow, especially the units that are somewhat affordable. The smaller ones produce only 5 to 6 gallons per 24 hours.
What is also important to understand, is that the quality of the water coming out of the reverse osmosis unit is determined by the quality of the membrane used inside of it. The better the semi- permeable membrane used, the better the quality of the effluent water, but the more expensive the unit will become. Good reverse osmosis systems, the ones that produce so-called ultra pure water, can easily cost around one thousand dollars. Not nearly within the budget we have planned for the small reef tanks discussed in this book.
For those interested in what osmosis and reverse osmosis are all about, and how the actual system works, we refer you to the in-depth discussion on the subject by Moe (1989) in "The Marine Aquarium Reference, Systems and Invertebrates", Green Turtle Publications, (obtainable from Aardvark Press as well).
Reverse Osmosis filtration is efficient in producing high qual- ity water, no doubt about it, but I strongly feel that we do not need such a set up in a small reef aquarium set up. If you already own such a filter, and if it was bought for prices around 100 to 200 dollars, you probably do not have all that good a unit, at least not of the quality just referred to. Check the effluent for nitrates, and especially for phosphates. Some ortho-phosphate may be left in the water, and organic phosphate will still be there as well. All is not wasted however .
If such is the case, the effluent may have to be treated again, or run through a different type of filter. We suggest that you use Poly Filters ordiscs. Also, if the reverse osmosis filter you are using lets such compounds through, you should consider doing away with it altogether and resorting to a less wasteful and more efficient method of pre-filtration, (see our suggestion later in this chapter). Water "is" a precious commodity. Preserve it.
An excellent way of treating water before it is added to the tank. Very effective at producing highly purified water. There are a few problems associated with using such a resin set-up however, especially at the Hobbyist level.
Resins only have a limited ability to remove impurities; to clarify this means that they can only absorb-adsorb a certain amount of them, and then they become ineffective. View resins as highly porous materials that have an enormous internal surface area. When the surface area is filled so to speak, no further impurites can be removed from the water, and the resins stop working, and need to be cleaned.
That is where the problem starts, for most hobbyists anyway. To recharge resins, special treatments need to be performed, and these treatments require the use of rather strong chemicals. Not everyone is prepared to take the time to "re-charge", as it is called, the resins, and not everyone is prepared to handle the chemicals that are necessary to do so, either. Moreover, a lot of Hobbyists who are unfamiliar with chemicals, should not use them to begin with.
Although de-ionization is very effective,and certainly rec- ommendable, we prefer you to stay away from it if you can. Resort to other methods, easier to implement, and not so cumbersome in their use, especially the regeneration part, which requires that you keep chemicals around that can be dangerous if not used properly, or if they fall into the hands of children, who do not know how about them, and could get seriously hurt as a result. I am not saying "do not use this process", but I am definitely alerting you to the potential problems that surr- ound this form of water purification. In fact, because we sell de-ionizers at my company, and in light of what we have just said, we offer a re-charging service for resins, so Hobbyists do not have to do it themselves.
Again, these comments lead us to a simpler filtration set-up, one we will describe a little later in this chapter, and the one I use myself to prepare water for our tanks. I sometimes use de-ionization as well, but only if I need water for very special purposes, e.g. when testing chemicals that are used in products that my company manufactures, when I want to be sure the water we need, does not contain any elements that may interfere with the working of the various compounds and products being tested.
Resin filtration can take on many forms. Details can be found in my other books, and also in our Newsletter Marine Reef, Volume 1, Numbers 20 and 21. Dozens and dozens of different resins exist and are manufactured by many companies , Rohm and Haas being perhaps the best known one. Each resin, or each set of resins, as two are normally required, is meant to perform a specific task. To do the job, therefore, you need very specific resins, not just any type. This is often overlooked by the Hobbyist, or small manufacturer, who is eager to have a product, and does not invest in the necessary research to end up with the right resin for salt water reef tank applications.
Keep in mind too, that you cannot use de-ionizing resins in salt water. Ionic competition, especially from the compounds that are pre- sent in salt water in great quantities such as salt (sodium), interferes with the process. This coats the outside of the resins very quickly, and as a result, they become totally "blocked" so to speak, and do not perform the task you obtained them for anymore. You have, in essence, wasted your money, and may have a false sense of security, thinking that the resins are in fact cleaning your water.
UV sterilizers have been around for quite some time, and are meant to kill bacteria and other undesirable very small life forms in the water. As such, U V sterilizers can play a role in pre-treating the water.
Since I have already pointed out that a micron filter of a small rating can do the same job for you in a much easier fashion, my recom- mendation is that, if bacteria, protozoa and parasites are a concern, use a sub-micron filter. It is simple to install, easy to clean and main- tain, and inexpensive on top of it.
Ultra-Violet Sterilization equipment also brings about a set of problems that need to be dealt with for the unit to operate efficiently. For example, the water must flow slowly through the housing, and very closely to the bulb itself; the latter must be jacketed in a quartz sleeve, for optimum efficiency, as quartz glass lets UV rays through. The "wattage" of the bulb(s) must be accurately decided upon. Bulbs need to be changed frequently, and need to preferably operate at a temp- erature exceeding 100 degrees Fahrenheit. If operated at the temp- erature of the tank water, the bulb is nowhere near as efficient.
For pre-filtering water, this is not at all a practical solution, in my opinion, and I have therefore not included it in the suggested pre-filtering set-up discussed later.
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