Why Have A Filter?
Because we keep fish in an enclosed area eg a tank there is nowhere for their waste to go. In effect they are swimming around in their own toilet. The purpose of a fish filter is to take the harmful effects of fish urine and faeces out of the water. If fish are swimming around in their own poisinous waste they are going to become listless, sit at the bottom of the tank occaisionally going o the surface to gasp air and then finally die.
How does a filter work?
Fish filters use naturally occuring bacteria to break down the fish waste and turn it into plant food. This sounds like a miracle but if you think horse manure - compost tip - plant food its the same principle. Very basically bacteria turn waste into ammonia then nitrite and finally nitrate. Some filters incorporate charcoal which takes out heavy metals and other harmful material. The best also incorporate zeolite which locks up ammonia.
Will a filter cure my cloudy water?
Cloudy water is always caused by overfeeding. Fish require very little food and have very little ability to store extra food as fat (you have never seen fat on a piece of haddock). This means that they excrete excess food which turns the water cloudy. If you underfeed your fish they will take weeks to die and you will see them get thin first. If you overfeed your fish you can kill them in a day. Fish need constant refueeling so cut down on the amount of food you feed not the number of meals. Feed two or three times a day but only give small amounts. Don't put extra in because some fish seem to get the food before others. They will get their share if you feed properly and regularly. The secret is little and often. Better quality foods are more digestible and so the fish produce less waste. This means your filter works better.
The bneficial bacteria is not instantly available it takes up to three weeks to develop. When first setting up a tank or installing a new filter there will be more fish waste than bacteria to eat it. This is why you must not overstock a new tank. Start with only one or two fish building up stock slowly over three to four weeks. All good fish shops will test water for free if you are buying fish so take a sample of tank water in to your local store before buying fish or buy a test kit.
Nearly all water in the UK has chloramine in it. This is a chemical put into our water to kill bacteria. The reason you can't drink the water in Spain is because it is not chlorinated. Chlorine and Chloramine will kill the bacteria in you filter. If you clean out the filter in tapwater the bacteria will die. Filters need cleaning every couple of weeks. Also to avoid unsightly green algae it is necessary to cahnge 25% of the tanks water every fornight. The best thing to do is empty a quarter of the tank into a bucket and then clean the sponges out in the tank water. You must then treat some new water with a dechlorinator before using it to refill the tank.
Undergravel Vs Powerfilters.
Neither are better as they both use the same bacteria. Some powerfilters work by trickling the water over the filter which hangs on the side of the tank or is contained within the tank lid. These work best of all as high oxygen levels allow more classes of bacteria to develop.
Do I need an Airpump.
If you have the correct sized filter an air pump is not necsessary. Airstones help to move water around the tank releasing some gases earlier and improving the growth of bacteria. They are beneficial but not essential.