The ultimate recipe for a successful sweet water aquarium (part 2)

The filter

The filter, whatever may be, must not filter water, but only circulating it !

Empty your filter fron watever is inside for filtration and fill it with porus ceramic or clay material.
The aim is to create as much surfice area as you can, so beneficial bacteria can grow on it.
The bacteria, in turn, will purify your water from fish waste or uneaten food.