Systems - The Structure
Filtration - Do It Yourself
Written by Tuesday, 16 January 2001 01:00
The average commercial filters either have limited capacities, or they do not have the utilities of a self-made filter. So what does an aquarist do when he has to support a tank with a larger water volume than usual? What can you do if the tank you want to support demands some functions that the filters on the market do not have? Or perhaps there are filters that look capable to run your tank, but their cost is more than you can afford. Then: Do It Yourself.
First of all, you have to know what kind of tank are you going to run, which filter type are you going to use, and which way are you going to install it in your system. There are three types of suitable filters. One type can be put inside the tank, while two others can be installed outside the aquarium. These filters can be built in one narrow side or in the back of the tank and covered (there are many ways and materials for such purposes) and can easily be made from glass plates. The inside self-made filter can be an ordinary internal filter with at least four compartments (maybe five for marine tanks). The inlet of such a filter can be at the lower part of the water column, or both the lower and the upper parts, or, finally, we can manage the filter to utilize the entire water column. We achieve this by letting the water pass through openings at the front glass plate, then through screens in the filtering area. We can force water to pass trough the media compartments with a snake like movement, either vertically or horizontally.
The advantage of the horizontal way, if the inlet of the filter is the entire water column, is that we may run the tank with the water at a very low level, as long as the water pump that returns the water to the tank after its travel through the media is submersed. We can use this utility in order to make a special treatment (bath or dip) or just to use less drugs for less water volume. The first chamber is used for mechanical filtration, so we fill it with aquarium moss or suitable sponges. We put the chemical media filtration in the second chamber and porous materials, for the nitrifying bacteria colonies, in the third one. The last compartment houses a water pump with a turnover rate of three to five times the total water volume per hour.
The volume of the biological substratum must be at least 17% of the water volume we have to deal with. For a marine tank, a fifth compartment must be in between the mechanical and the chemical media compartments, as well as have the skimmer installed in it. An efficient skimmer device must have twice the capacity of the water volume we want to skim and the venturi skimmers are preferable. We can maintain wet – dry procedure within the tank if we force water to pass through the biological chamber from a higher level through a narrow opening and via the screen with holes drilled on it. We can make the water travel both vertically and horizontally in this case, and the volume of the biological substratum can be from 2% to 8% of the total water volume instead of the 17% that we must use in the first case. We can install such filters outside the aquarium, either over or under the tank. The over tank filter is by nature a wet – dry one, because the water that is driven from the tank up wards to the filter body returns to the tank with the help of gravity. So if we force water to pass from the top side of the filter through a screen with holes drilled on it, and we put three traces so that water can pass through them, and have one filtering media under the other (the first with mechanical media, the second with chemical media and the third one with some suitable media to get colonized from nitrifying bacteria), keeping some distance between them, then water shall return to the tank from the bottom side of the filter from a hole we have drilled on the bottom glass, forced by its weight. The media are not submerged but water drips like rain through them and continues to drift back to the tank.
Always, the outlet of a filter like this has to be twice the inlet, and if it is designed to be covered, then an air hole has to be drilled on the cover glass to suck air into the media container. The same way, we build a sump (this is the name for a filter placed under side the tank). In this case we drive the surface water through an overflow to the first (mechanical) chamber of the filter. We have to calculate the water volume that is driven in the filter through the overflow, so we shall build the filter tank big enough to hold this amount of water without the fear of overflowing and turning our house into a pond in the case of power failure, which would cause water pump that returns filtered water back into the tank to stop. So, after the mechanical filtration, the water passes through screens to the chemical media chamber, the biological substratum, and finally to the water pump’s compartment that is employed to return the filtered water back into the tank.
We can build (for marine tanks) a skimmer chamber in between the mechanical and chemical ones, and, of course, we can build it (as mentioned above) in a way that the biological substratum is not submerged but in a wet – dry condition. If you decide to run your tank this way you will have the opportunity to build a powerful polymorphic filter suitable for keeping your system clean and clear with less money that you would spend buying and installing one or more of the available commercial filters.
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