25 Algae filter

The algae filter is a closed bio filter filled with a filamentous or macro algae species. It is used to reduce (assimilate) nitrogen (nitrate) and phosphorus (phosphate) The most popular species used is the wire alga Chaetomorpha spec.. The algae filter is a passive filter. The algae filter stage can alternatively be placed in a chamber of the filter tank. Lighting is necessary. The excess algae must be removed regularly.

Like a refugium, it can be lit at night and attenuates the daily pH fluctuations. The nocturnal oxygen deficiency in skimmerless aquarium systems is also reduced.