12 Filter cotton wool / filter sponge

Filter cotton wool or a filter sponge can be used to remove medium to coarse particles and fibers from the water. They thus belong to the group of particle filters.

Similar to sock filters, filter elements with filter cotton or a filter sponge should be built into the system in such a way that a quick and thus regular washout is carried out. A pot filter commonly used in freshwater aquaristics should only be used as an exception.
If the pollutants accumulate for a longer period of time, bacterial degradation reactions begin, which can lower the redox potential (ORP) and lead to further undesirable consequences.

Small filters filled with filter cotton wool can be installed without hesitation as particle traps upstream of valves with very low flow rates (for example, to control the water inflow for nitrate filters). The low capacity of contaminants is inconsequential for the aquarium environment.

Filter sponges are often used as the top layer in the overflow chamber of the aquarium to reduce the overflow noise. It retains the very coarse substances (algae, fibers). This sponge should also be cleaned regularly.