Freshwater Aquarium Filters - The Right One For You
Why do you need an aquarium filter?
The freshwater ponds and lakes of the world are big enough to reach a biological balance. Meaning that the size of the fish population adjusts to conditions and the waste is all dealt with biologically there being no build up of ammonia, nitrites or nitrates.
Aquariums are not big enough to reach equilibrium withiut a great deal of help. The water would very soon become toxic and all the fish would die without external help. It is because the fish density that we like to have in our aquariums is greatly in excess of that found in nature. Fish in such high numbers produce far more waste than the resident bacteria can possibly cope with so even changing one third of the tank water every week is not sufficient to keep the water clean. In addition it is imperative that you have a freshwater aquarium filter of some kinf.
How do Freshwater Aquarium Filters work?
Any filter system that you consider should be able to perform in any of three ways - mechanically, biologically and chemically. A fourth way also exists called germicidal or algaecidal, this kind of filtration is usually applied for a particular purpose like getting rid of green water and utilises a UV steriliser.
Mechanical filtration involves using foam and/or fibre to remove large particles like uneaten food and fish waste. The filter medium is graded from coarse to fine the coarse removing large particles and the fine removing small particles.
Two type of good bacteria are used in biological filtration. Fish excreta turns into ammonia which is very poisonous to the fish. Together, the two types of bacteria convert ammonia to nitrite which is in turn converted to the much less dangerous nitrate. The nitrate concentration is kept down by means of regular water changes.
Chermical fiters invariably use activated charcoal or various resins. Chemical filtration is usually only necessary when the tank is first setup.
The Five Main Types of Aquarium Filters
1.Amongst the first filter designs are the in-tank filters also known as corner or box filters. Most of the modern filters used today are based upon these filters. They work by pulling water through several different filter media using an air pump. They are not expensive but their performance is not that great when compared with other filters. The most common uses today are for breeding and hospital tanks.
2. Undergravel filters (UGFs) comprise a grid of plastic pipes with small holes every centimetre or so. The gravel or substrate sits on top of the grid thus creating a water space under the gravel. The pipes are all connected to up to four ‘air lifts’ which slowly pull detritus and debris down through the substrate. The idea is that bacteria can break it down there. Under gravel filters are cheap to buy and not difficult to setup and run also they use an air lift to pull the water through them so oxygenation is high. One of their disadvantages is that they do not enable chemical filtration. Also the small holes in the pipes are easily blocked and then waste tends to build up in the substrate. It is therefore necessary to regularly use a siphonic hoover on the substrate and two or three times a year to properly clean the filter. To get at the filter you have to remove all of the substrate. Because of this fact alone, under gravel filters have become less common.
3. A much better choice are cannister filters. These units consist of a canister and pump with a siphon tube to pull water out of the tank and a return tube to pump the water back in. Usually the canister contains coarse ceramic 'donuts' or a coarse fibre, perhaps some chemical filtration medium like charcoal, porous glass or stone for biological filtration finished with a very fine filter fibre. Biological, mechanical and chemical filtering are all perfomed by a cannister filter. Most canister filters are very thorough and do a great job keeping aquarium water clean. These filters do have some disadvantages, they tend to be expensive and the filter media is not cheap also they have to be maintained every month. If they are not maintained well they can become nutrient traps. Fouled filter media results in nitrogenous waste being pumped back into the tank rather than being removed. This results in algae bloom and poor water quality! It is also necessary to add a pump and airstone to aerate the water since cannisters are competely closed. Overall though, when properly maintained, a good canister filter is hard to beat.
4. Power filters hang on the outside of the tank and use a pump to pull water up into the filter. The water falls back into the aquarium after having passed through mechanical, biological and possibly chemical filter media. These filters are rapidly gaining popularity with aquarists because they are efficient, slightly less expensive than canisters, and a dream to maintain. They help to oxygenate the water because they are exposed to the air. The oxygen-rich water helps support huge populations of nitrifying bacteria making power filters some of the most efficient biological filters. The biowheel version is particularly good.
5. Wet/dry or trickle filters. These are only mentioned for completeness. Their use is normally limited to very large tanks. They are expensive and if they go wrong can empty your tank!
Conclusion
Regular water changes are not enough to prevent a build up of toxins in the water which will kill your fish, you also need a good filtration system. The several choices have been described above. The choice is yours.
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