Unfortunately for fish they live in their own toilet! In order to keep the water clean and pure in your aquarium you will need a filter. Inside the filter good bacteria will build up which will break down the particles that will prove harmful. There are many different types available but they all fall into two main categories.
An internal filter is a device which sucks in water and then expels it. While inside the filter the water passes though sponges which collect the particles in the water which will be harmful for the fish. The internal filter is placed inside the fish tank and needs to be plugged into a mains supply to power it.
The other way of keeping the water clear is to use an under gravel filter. This device is placed under the gravel in your tank and is powered by an air pump that sits outside the tank. Water is sucked though the gravel and the gravel traps the unwanted particles.
© Fresh Water Fish Keeping.com 2006
