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3.3.1 THE FILTER ITSELF:
The filter can be round or rectangular, or square, or any shape for that matter. As long as you can fill a portion of it with an appropriate biological filtering material, the shape has no bearing whatsoever on the efficiency of the filter, except perhaps for one fact: it should not be too narrow. If such were the case, channeling would occur and the water would not be dispersed properly over the medium. Channeling is a process where the water flows too much along the side walls of the filter and not enough over the biological medium inside the filter chamber.
In the same manner as shape is irrelevant, the material out of which the filter is made is not important either, except for the fact that it must be saltwater resistant, and can not leach any noxious compounds into the water. Trickle filters can, therefore, be made out of glass, acrylic, pvc, cpvc, polycarbonate, polyethylene, polypropylene and so on. You could, conceivably, build a filter out of wood that has been coated with polyurethane (several layers), or 316 SS, or some other saltwater resistant metal. The one constraint that results in most filters being built out of glass, or acrylic, is price. Indeed, most of the other materials mentioned would price the filter out of the market. Just think of 316 SS, nylon, Teflon, and titanium, for instance.
Practically speaking filters are made out of glass and some type of acrylic, and are, usually anyway, rectangular and upright L-shaped. The size of the filter is entirely a matter of the size of the aquarium on which the filter will be used and how much biological filtering material it must hold as a result. Suggestions on how to evaluate both the type of material and the quantity needed for various size of aquariums, at various levels of biological load, are given elsewhere in this book. You should compare the suggestions to what you are doing now, or intend to do on the aquarium you are setting up, or planning to set up.
Water flows though the filter from top to bottom, and collects there before it is returned into the main water stream back to the aquarium. We call the bottom of the filter, the sump. A large sump is a benefit, as it increases the total amount of water in the system, and allows for the addition of optional equipment.
To disperse the water over the biological medium, a spray bar, or a drip-plate, is used. Both have their merits, although I personally prefer the drip plate. It allows for a more even and continuous distribution of the water, and is not subject to stopping, a problem spray bars have had ever since they were introduced, and still have today, even though some manufacturers keep claiming theirs won't.
Even if they do not stop, they will often slow down significantly, and diminish the efficiency of the water distribution over the medium, as a result. Remember, the better the water distribution over the medium, the better the filtration. Additionally, the better the distribution over the medium you use, the less of it you will need. The latter should be pretty obvious - if you use a medium more efficiently, you need less of it - and good enough a reason to make sure that such efficient water distribution exists at all times.
The biological filtration that takes place in a trickle filter is an "aerobic" process, meaning it requires oxygen. In fact, it requires a great deal of oxygen (Hueckstedt, 1968, 1976). Providing a supplemental source of oxygen is, therefore, an excellent idea. This is done by equipping the filter with air inlets that allow the hobbyist to blow air (a mixture of a number of gasses, and amongst others, oxygen) into the biological chamber. This results in two positive, beneficial, actions:
Both these actions are beneficial to the overall water chemistry and the well being of the lifeforms you keep in the aquarium. Higher dissolved oxygen levels reduce stress on animal life, and more oxygen in the biological chamber, results in a stronger and more potent colony of bacteria. This, in turn, improves the quality of the water and reduces stress as well. Better water quality = a more vibrant looking aquarium.
Basically that is all there is to a trickle filter: (a) water enters at the top, (b) is dispersed over (c) an adequate medium, (d) bacteria grow on that medium and (e) convert ammonia to nitrite, and (f) nitrite to nitrate. (g) The water collects in the sump of the filter, and (h) is returned to the tank by means of a pump. The process is continuous and automatic, insomuch as water is continuously brought down to the top of the filter, and returned to the aquarium after it has passed through the trickle filter's biological chamber.
Because it is critical that this process not be interrupted, the pump(s) used on the system must be of superior quality. Indeed, they have to run 24 hours a day, day in day out, for weeks, months and years in a row. Skimping on the cost of the pump is, therefore, a big mistake, but one that is often made in an effort to reduce the cost of running the reef. The life of your tank, and what's in it, depends on it.
Interrupting the process results in:
Spend a little more on the pump than you intended to. Buy the best pump you can afford. It will pay for itself in the short run because the quality of the water will remain where you need it, resulting in less fish and invertebrate losses, which can quickly eat up the savings you would have made if you had bought a cheaper pump. I speak from experience talking to many hobbyists who have made the mistake.
Some hobbyists want to build their own filters. There is, theoretically, nothing wrong with that, except that, in my experience, practically 9 times out of 10 such filters do not perform as required. Only after you have had a good quality commercial unit for some time, and have studied it, and figured out why it is performing the way it is, taking all the small detail into account, will you be able to build a unit yourself that works satisfactorily.
Unless you already have this experience, we suggest that you stick with commercially available filters. Many make the mistake of just copying filter components, without really paying attention to detail, and often the latter makes the difference. Copying components of a filter does not necessarily mean that you have copied the principles, and added the necessary detail to make the unit efficient. Proportions of various components, small features that may not be transparently obvious to you, exact sizes of holes and their positioning, are all important, and differentiate a basic filter from a real efficient one.
Additionally, building a unit on a trial and error basis will cost a lot of money in the long run, and may not make it any less expensive that a good quality commercial one to begin with. An error that is frequently made by hobbyists who build their own filters, is mixing parts and portions of different filtration systems, ending up with a hybrid system that may not be all that efficient anymore. Often existing components of a system are meant to work together, sometimes synergistically. Using only parts of such systems, and/or combining parts of several systems may do more damage than good, and often results in a filter that controls you, rather than the opposite. Moreover, if something goes wrong, who do you call? And what will the company you call say after they find out that you have, in fact, mixed several approaches to filtration? Think about it. How would you react if you were in their position?
We mentioned pumps briefly, and suggested that you should buy the best pump available for the size system you run. Because such pumps can cost a fair amount of money, it is a good idea, and suggested, to protect it with a good quality float switch to prevent it from running dry and burning out. Float switches serve a second purpose: they even out the amount of water that goes up and the amount that comes back down to the filter. For example, if the amount of water going up to the tank is rather high, and the method used to bring water back down to the filter (the siphon, or overflow corner arrangement, etc. as we shall explain somewhat later), is somewhat slower, the water level in the sump will have a tendency to lower itself (more water is going up than coming down).
Without a float switch this can lead to:
All these can be prevented by using a float switch. Several such switches are now on the market: a German unit made by ELB, orange in color, cigar-shaped and about 4 to 4-1/2 inches long, Rule-O-matic switches that can be found in marine supply shops, stainless steel ones that are advertised in catalogues such as McMaster Carr and W.W. Graingers, and a switch sold by Thiel Aqua Tech, the Super Float, able to handle loads of up to 6 amps. Many Reed switches are advertised in catalogues but do not usually fit the hobbyist's requirements because they cannot handle the amperage developed by the pump(s) used. Always check that the switch you buy is rated for both 115 volt and the amperage your pump develops. If not, you will ruin the switch.
As systems get more sophisticated they require more intricate piping. This may mean that you will have to use flow and check valves, fittings to divert water to certain optional equipment you are using, flow meters, solenoids, and so on. The more intricate the piping, the more expensive the system will obviously get. Although ball and check valves can be ordered at fairly reasonable prices from mail order companies such as U.S. Plastics and Savko, solenoids, flow meters and other such equipment can be fairly expensive. Later on we will review some of this equipment, but you can find a detailed look at such advanced aquariums in Advanced Reef Keeping Made Simple (I), Thiel 1989, and _Small Reef Aquarium Basics_, Thiel 1989, both published by Aardvark Press.
Many filters you will see on the market have a space provided for a foam block. The reason for this, we assume, is that early pictures and drawings of such filters always showed such a compartment. The idea was to fine filter the water on one hand, and provide an area for some amount of controlled assimilation/denitrification on the other (reduction of nitrates in the water). As time went on, I have found that these compartments are a good feature, but can be improved upon by using a better way of filtering the water: a foam cartridge, hooked up to the pump intake, on the inside of the sump of the trickle filter. In this manner, all the water in the sump must first go through that foam cartridge before it can re-enter the main water stream. Such foam cartridges are standard in both the Platinum series, and the Summit Aquatics trickle filters.
The problem with the foam blocks is that water having a tendency to seek the path of least resistance, the water will flow by the foam block and not through it, greatly reducing the efficiency of the setup. Some filters have the foam installed in such a way that all water must pass through it. Such is an improvement, but requires that the hobbyist pay careful attention to its cleanliness, as the foam will plug up rather quickly, creating an uneven water level between the back and the front of the sump. Those of you who have such a setup may have experienced this already, and know what I am describing. Foam cartridges in which the water is "sucked" through, because they are attached to the pump intake side work better, and need less attention. Cleaning them once a week is usually fine, and easy to include in the weekly maintenance schedule of the tank.
Alternatively, the prefiltering should be done in the main water line, between the trickle filter and the aquarium, by using some form of canister filter, for example: Lifeguard, PEP, etc. Special purpose filters designed to fine filter are also available, for instance the Fin-L-Filter from Poly Bio Marine Inc. (pronounced: final filter). Of course, the siphon bringing water down to the trickle filter, or the corner overflow box arrangement, should also contain some prefiltering material to prevent dirt from getting into the biological chamber of the trickle filter.
This is especially so if you are using a material in the biological chamber that easily traps dirt, such as, for example, D.L.S. (Double Layered Spiral) or Biopaks, or shotgun wadding, plastic hair curlers and so on. Plugging of that material will give rise to a number of problems that are detrimental to the water quality. The scenario is as follows:
Not a very positive scenario. Cleaning any of the materials mentioned above is difficult and brings about other problems:
It should be fairly obvious, in light of all of this, that you will need to use a filtering material in the trickle filter that does not trap dirt, or at least lets it get through easily and end up in the sump where you can remove it later on, for instance during your next scheduled maintenance session. More on this in the next few pages when we talk about the required minimum amount of biological surface area.
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