Why you need filtration

Mechanical filtration is the straining of solid particles from aquarium water. This doesn't directly remove dissolved ammonia, nor does it remove microscopic bacteria and algae from the water or any solids trapped by gravel, plants, or decorations. Nevertheless, it is an important part of keeping your aquarium clean and your creatures healthy.

The four most popular mechanical filtration media are 1) sponges, 2) paper cartridges, 3) loose and 4) bonded floss media which are reusable to different degrees. Clean paper cartridges have the smallest openings and clean bonded floss has the largest openings. Clean sponges and clean loose floss fall somewhere between.

A filter media with small openings catches finer particles, but clogs faster. Also, as a rule, a physically large filter area will clog more slowly than a small filter. As the filter media gets dirty it will trap smaller and smaller particles. At some point the media is so clogged that it will not pass water.

SUMMARY: A good mechanical filter is one that traps enough solids to keep the water clear without plugging too often.