There are several ways of improving filter, such as adding a U V system, or enlarging your filter. Simply placing more filter medium in your filter will help, but the latest idea to start catching on with the trade at least is the installation of settlement tanks.
As everybody knows if you pump water down a narrow pipe under pressure it will carry fine particles with it. When the water slows down, as it does when it enters a filter box, some of the suspended matter will settle out. This can be seen by the amount of muck that accumulates at the bottom of the filter after having passed through the foam, or nylon brushes. The more muck that goes into your filter the more often you will have to clean it out. The best thing is to have the bulk of the suspended matter settled out before the water enters the filter. This can easily be done by the addition of a settlement, or vortex tank. This is simply a round, or even conical tank through which the water from your pool passes. The water is pumped in half way up at an angle so that it causes a current in the tank. The water spirals round and round rising up the tank and is piped out at the top. The heavier sediment laden water slowly sinks and the particles settle out at the bottom of the tank forming a thick sludge which can be piped off with a bottom drain, or tap.
It is possible to buy ready made settlement tanks constructed from fibre-glass but they are very expensive. It is a relatively simple job for a keen D.I.Y.’er to make one out of a rain-water barrel. The pipefittings need a good seal, which is not easy with a round barrel, but a tube of aquarium sealant should solve any problems. Installed correctly a settlement or vortex tank can improve water clarity considerably on an overloaded filter system and can cure brown water completely.