A filter is a must for every tank. A filter provides a system of weeding out clumps of old food and other debris floating around the tank. It also is a place where good bacteria thrive and grow. The good bacteria that grow next to the moving water on your filter act as a filter themselves, purifying fish waste from the water and breaking down bad chemicals like nitrogen.

The different types of filters are sponge filters, and other filters. Different types of tanks and fish work with different types of filters. For a standard 10 to 20 gallon size tank, often a ____ filter works the best. 

Most filters come with replaceable filter cartridges. Carbon inserts come in many models too. The carbon absorbs waste from the water, but only for a period of a few weeks. After that, if you do not remove the carbon, it may start to put the waste back into the water. 

Most filters will say to change your filter media every 2 or 3 weeks. This is not necessary. You must change or rinse your filter when it becomes clogged and water cannot pass through it. It can take up to 4 weeks for the beneficial bacteria to build up in a new filter. This bacteria is working to keep your fish safe and keep the harmful chemicals down in your tank.

For your filter to become clogged, it would take much longer than a few weeks. Rinse it with tank water. If you rinse your filter media in the sink, the cholrinated water will kill the beneficial bacteria and you may experience fish loss because of high nitrogen levels in the water.