Why do you need an aquarium filter?
An ecological balance is achieved by freshwater lakes and ponds because they are on the large side. By that I mean that they are able to reach equilibrium whereby the fish population adjusts according to conditions and fish excreta is all dealt with biologically and there is no build up of ammonia, nitrites and nitrates making the water poisonous to fish.
Fish tanks are too small to reach a balance without help. The fish would very quickly die from toxic water 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. Even changing one third of the water every week is not enough to keep the water safe because the resident bacteria cannot possibly deal with the amount of waste that fish in such high numbers will produce. You must have some sort of freshwater aquarium filter system as well.
How do Freshwater Aquarium Filters work?
Any filter system worth its salt should be capable of performing in all 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 waste converts to ammonia which is very toxic. One kind of bacteria converts the ammonia to nitrite and the other kind of bacteria converts the nitrite into the much less dangerous nitrate. Nitrate levels are kept to an acceptable level by regular water changes.
Chemical filtration usually uses activated charcoal and/or various specific ion exchange 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. They are amongst the first filter systems produced and and are the starting point of the modern filters that exist today. Normally powered by an air pump they work by pulling water through a variety of filter media. Compared with other filters available they are not very effective but they are reasonable in price. Breeding and hospital tanks are there most common use today.
2. Undergravel filters (UGFs) comprise a grid of plastic pipes with small holes every centimetre or so. This grid sits under the gravel or substrate of the aquarium, creating a space of water beneath the gravel. Water is slowly pulled through the gravel into the filter pipes by up to four ‘air lifts’. The theory is that bacteria will 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 disadvantage is that they normally do not do chemical filtration. In addition to this, the small holes in the pipes can easily get blocked and waste tends to accumulate in the gravel. As a consequence you must regularly use a siphonic hoover on the gravel and at least twice a year completely clean the filter. To get at the filter you have to remove all of the substrate. Undergravel filters, for this reason alone, are becoming less popular.
3. A much better choice are cannister filters. These units comprise a canister with a pump inside and a siphon tube pulling water out of the tank and a return tube to pump the fitered water back in. The typical canister normally contains some type of coarse mechanical media, like ceramic “donuts” or very coarse fibre, some chemical media like filter carbon, some porous glass or stone for biological filtration, and finally some very fine filter fibre. Biological, mechanical and chemical filtering are all perfomed by a cannister filter. Cannister filters are very powerful and easily keep your aquarium water clean. The downside to these filters is that they tend to be expensive, use expensive media, and need to be maintained every month. If they are not maintained well they can become nutrient traps. This means that all of the fouled filter media actually begins adding nitrogenous waste back into the water instead of removing it. Poor water quality and algae bloom are caused by it! It is also necessary to add a pump and airstone to aerate the water since cannisters are competely closed. Provided it is well maintained a canister filter is probably one of the best filters.
4. Power filters use a pump to pull water up into the filter which hangs on the outside of the tank. The water then passes through mechanical, chemical, and biological media in various configurations, then spills back into the aquarium. These filters do a good job, are cheaper than cannister filters and are a dream to maintain because of this they are quickly gaining in popularity. They help to oxygenate the water because they are exposed to the air. Power filters are very efficient biologically because they are open to the air so the water passing through is oxygen rich and supports large numbers of nitrifying bacteria. Particularly good is the biowheel version.
5. Wet/dry or trickle filters. They are only included for completeness. Their use is normally limited to very large tanks. They are not cheap and can empty your aquarium if they go wrong!
Conclusion
In addition to changing one third of the tank water every week, you also need an efficient freshwater aquarium filter system to prevent a build up of toxins in the water which will eventually kill the fish. The possible options are outlined above. It’s your choice.
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