| Why do you need an aquarium filter? | | | | Under gravel filters use an 'air lift' to pull water |
| Freshwater ponds and lakes of the world are large | | | | through them so oxygenation is high other |
| enough to achieve an ecological balance. By that I | | | | advantages are that they are cheap to buy and easy |
| mean that they are able to reach equilibrium whereby | | | | to setup and run. One disadvantage is that they |
| the fish population adjusts according to conditions | | | | normally do not do chemical filtration. Also the small |
| and fish excreta is all dealt with biologically and there | | | | holes in the pipes are easily blocked and then waste |
| is no build up of ammonia, nitrites and nitrates making | | | | tends to build up in the substrate. So you have to |
| the water poisonous to fish. | | | | remove the filter two or three times a year to give |
| Aquariums on the other hand are a microcosm of the | | | | it a good clean as well as regularly use a siphonic |
| natural world and need a great deal of help to | | | | hoover on the gravel. This means that you have to |
| achieve any kind of equilibrium. Without external help | | | | remove most of the substrate to get at the filter. |
| the water would very soon become foul and kill all | | | | For this reason alone, undergravel filters are becoming |
| the fish. The usual reason is that the fish density | | | | less common. |
| found in our ponds and lakes is much less that what | | | | 3. A much better choice are canister filters. A siphon |
| we like to have in our aquariums. Even changing one | | | | tube connected to a canister and pump pulls water |
| third of the water every week is not enough to | | | | out of the tank and through the canister and a |
| keep the water safe because the resident bacteria | | | | return tube puts the water back in. Usually the |
| cannot possibly deal with the amount of waste that | | | | canister contains coarse ceramic 'donuts' or a coarse |
| fish in such high numbers will produce. Consequently a | | | | fibre, perhaps some chemical filtration medium like |
| freshwater aquarium filter system is essential. | | | | charcoal, porous glass or stone for biological filtration |
| How do Freshwater Aquarium Filters work? | | | | finished with a very fine filter fibre. A canister filter |
| Any filter system worth its salt should be capable of | | | | therefore performs all three kinds of filtering. Canister |
| performing in all three ways; mechanically, biologically | | | | filters are great at keeping your tank water crystal |
| and chemically. A fourth way also exists called | | | | clear. The downside to these filters is that they tend |
| germicidal or algaecidal, this kind of filtration is usually | | | | to be expensive, use expensive media, and need to |
| applied for a particular purpose like getting rid of | | | | be maintained every month. If they are not |
| green water and utilises a UV steriliser. | | | | maintained well they can become nutrient traps. The |
| Large particles like food waste and fish excreta are | | | | result is that nitrogenous waste is pumped back into |
| removed mechanically by foam and/or fibre filtration | | | | the tank because of the dirty filter media. Poor |
| media. The filter medium varies in texture from | | | | water quality and algae bloom are caused by it! Also, |
| coarse to fine, large particles are removed first by | | | | since canisters are completely closed, they do not |
| the coarse filter and then small particles are removed | | | | oxygenate the water so it becomes necessary to |
| by the fine filter. | | | | add an airstone or perhaps a small water pump to |
| Two type of good bacteria are used in biological | | | | agitate the water surface. Overall though, when |
| filtration. Fish waste rapidly turns into ammonia which | | | | properly maintained, a good canister filter is hard to |
| is extremely toxic to the fish. Between the two | | | | beat. |
| kinds of bacteria ammonia is converted to nitrite and | | | | 4. Power filters hang on the outside of the tank and |
| then nitrite is converted to the much less toxic | | | | use a pump to pull water up into the filter. The water |
| nitrate. Water changes then keep the nitrate levels | | | | falls back into the aquarium after having passed |
| down to an acceptable level. | | | | through mechanical, biological and possibly chemical |
| Activated charcoal or ion exchange resins are used in | | | | filter media. These filters are rapidly gaining popularity |
| chemical filters. When the tank is first setup chemical | | | | with aquarists because they are efficient, slightly less |
| filtration is necessary but it is not normally required | | | | expensive than canisters, and a dream to maintain. |
| after that. | | | | Since they are exposed to the air they help |
| The Five Main Types of Aquarium Filters | | | | oxygenate the water. The oxygen-rich water helps |
| 1. Among the first filters to appear on the market | | | | support huge populations of nitrifying bacteria making |
| were the in-tank also know as box or corner filters. | | | | power filters some of the most efficient biological |
| Most of the modern filters used today are based | | | | filters. The biowheel version is particularly good. |
| upon these filters. They work by pulling water | | | | 5. Wet/dry or trickle filters. They are only included |
| through several different filter media using an air | | | | for completeness. Their use is normally limited to |
| pump. Compared with other filters available they are | | | | very large tanks. They are costly and have been |
| not very effective but they are reasonable in price. | | | | known to empty aquariums of their water if they go |
| They are commonly used today in breeding and | | | | wrong! |
| hospital tanks. | | | | Conclusion |
| 2. Undergravel (UGF) filters consist of a grid of plastic | | | | It is essential that you provide efficient filtration in |
| pipes with small holes every half inch or so. A space | | | | addition to regular water changes to stop a toxin |
| of water is created underneath the gravel because | | | | build up which will eventually cause your fish to die. |
| the grid sits there. Up to four 'air lifts' slowly pull the | | | | There are a number of different options which have |
| waste down through the substrate into the pipes. | | | | been outlined above. It's your choice. |
| The theory is that bacteria will break it down there. | | | | |