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Components of a Good Trickle Filter:
We already mentioned the biological compartment. Several features of this compartment are important, because they add to the efficiency on one hand, and to the ease of installation and servicing on the other :
Because acrylic warps easily when in contact with water, good reinforcements of the side of the biological compartment are very desirable. Beware of filters made out of very thin acrylic or similar materials. They will warp, and may split on you, unless reinforcements have been added to prevent this from happening.
A removable lid is a plus. Dirt will get into the top of the filter whether you like it or not. When the lid at the top is removable, it will be very easy for you to remove that dirt. The lid should also be reinforced, or made out of glass (best). If you can't get to the top, the dirt will do two things : it will decay and reduce water quality, and it will plug up holes in the drip plate (if that is what you are using, and you should).
At least two air inlets are recommended. The bacteria inside the filter are aerobic, meaning that they require oxygen to perform. Blowing a good flow of air into the filter is therefore very desirable. The better the air is spread out, the better the filter will operate. I usually recommend that Hobbyists use a air pump such as a Whisper 1000, or stronger (e.g. Wisa), and blow all the air inside the biological chamber, using both the air inlets. If only one is available, you may wish to drill a second one, push airline tubing through it, and then pack a little aquarium silicone around the hole, so no water comes out. Blowing more air will not hurt, to the contrary. To convince yourself of the benefit of doing this, run air into the biological chamber, note the redox potential, now shut off the air, and then watch what happens to the redox potential: it will go down (Bepko, 1988, Thiel, 1988). It may even go down quite a bit. You must blow the air into the chamber above the water level, directly into the column, not through an airstone placed in the water underneath the biological chamber.
The height of the chamber should be at least 12 to 14 inches. Shallower filters will work, but you will need to flow more water through them. Because there really is a limit to how much water can be flowed through a small biological chamber. Excessive current through the filter will wash off some of the bacteria, and result in a less efficient filter, less oxygenation, and a smaller biological colony.
The width of the chamber should be no less than 8 inches. Narrower filter chambers channel too much water on the sides rather than through and over the medium used, and that reduces the efficiency of the filter.
Use a filter with a drip plate rather than a spray bar. The reasons for this are explained in the section on drip plates, later in this section.
The chamber should not sit too deeply in the sump. This will keep all the medium out of the water in the sump. Bacterial beds that are out of the water are more efficient at handling ammonia and nitrite. Wolff (1984) suggests that the efficiency goes down to less than 60 percent when the medium is submersed.
Larger sumps are to be preferred. They increase the total volume of water in the the system, and make it easier for you to use a powerful pump. If too little water is in the sump, evaporation will lower its level quickly, and if, as you should, you are using a float switch, the pump will stop regularly, and eventually altogether when the water level is real low.
Larger sumps also have more space for other devices that you may want to add to your system and that you may wish to run with a power head.
The sump should preferably be reinforced too, as this will prevent warping and possibly splitting months down the road.
Compartments built in the sump are always a plus. They allow you to easily add certain compounds to the system. Make sure however that the compartments are built in such a way that the water coming from the biological chamber must flow through them, not just over them. Whatever you place in them will work better if the water has to go through the compound completely.
Depending on the size of the tank, you will be using a particular pump. Check the in and outlet sizes of the pump. Make sure the hole in the filter is of the same size, or larger, than the size of the pump intake. Re-drilling an existing hole is not the easiest and safest thing to do. If a bulkhead fitting is already included you will not have to go out an buy one. If you do, buy a real tank fitting, not a rigged male/female fitting type arrangement.
Built-in foam fractionators - protein skimmers - are a definite plus, but they must be of the size that your system requires. Not some flimsy little skimmer that was built to fit the filter rather than the tank! This is most important because undersized skimmers will be a real problem for the tank, and are one of many reasons for the appearance of red algae. See the section on skimmers for more details on sizing. Don't lull yourself into thinking that you have one if the filter you bought has a real small skimmer built into it. Stick with either an outside columnar one, or a built-in Venturi skimmer, and make sure that you can use ozone with it, because you probably will want to, or need to.
A sump with a slanted bottom will allow mulm and other detritus from being moved forward by the current, making it much easier for you to syphon it out. Mind you, mulm is technically speaking inert, and should not affect the water quality any longer, it is the detritus that needs to be removed.
Certain filters have a built-in tray for electrodes. That is handy if you are using them, but in the basic system that we are setting up, we will not.
Whether the sump has a lid, or not, does not really make much of a difference. Most of the evaporation is not from the sump, but from the aquarium itself. It makes the filter look more finished though.
From an economics standpoint this is a most important section. Buy a filter that is too large and you spend more money on the filter and also on the internal medium. Buy one that is too small, and your water quality will suffer, and you may lose fish, invertebrates, and ultimately money too.
In my estimation, buying the wrong filter will end up costing you two to three hundred dollars more than you should have spent. Of course, building your own filter would be the least expensive way to go. Plans are available in the magazines, and were also published in my other books.
The ultimate size of the filter will largely depend on the internals (biological medium) you use. The better the medium, the less of it you will need, and the smaller the filter will become as a result.
Here are my suggestions for sizing, providing you use either Bio-Techs, or Bio Blocks. Both are available from dealers nationwide, and cost about the same per gallon volume of the material.
The above numbers are lower than what you normally will find recommended because they are based on tests, not on advertising claims made by various manufacturers of plastic filtering media.
They assume you follow the directions in this book : most importantly that good dispersion is achieved by means of a "drip plate" of the kind we describe. This means that you may have to slightly modify (easy and explained later) the drip plate that comes with the filter you have bought, or are using now.
Why are these recommendations lower ? Over the last 5 years I have had the opportunity to personally use the following media: German blue balls, Jaeger Tri-Packs (2 sizes), Bio Cubes, Bio-Techs, Pall Rings, Norton Rings, Plastic haircurlers, EfigroB, Raschig rings, Bio Discs, Cut PVC pipe, Cut acrylic chips, Gravel trays, Sand trays, Beads, Dolomite, and others still.
Doing so gives one a pretty good experience with which materials provide the kind of filtration required for Marine Reef tanks, and allows for fair and educated comparisons of their respective merits.
The following criteria guided me in deciding which internal plastic medium to use myself, and recommend to others:
We have not recommended a product called pax, because it seems to trap more detritus than we feel is safe for your system. Unless some modifications to that material are made we feel that it is not a "best buy" for Reef tanks. It does well for fish-only tanks however. Biological filtration in Reef Tanks requires attention to details, not just "surface area" or "dispersion ability." Select what you buy very carefully.
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