Filter Wool

From RTAW Reefpedia

Filter wool can be a handy thing to have around with a marine aquarium. Its good at collecting undesirable particulate matter out of the water column, which is handy if you have a spawning incident, sandstorm, or something sucked through a powerhead.

It is often used above trickle filters to prevent buildup of detritus in the bioballs and prevent "clogging" resulting in loss of surface area.

However like any form of mechanical filtration (other than protein skimmers) there are negatives to regular use. There are many free swimming beneficial organisms in the aquarium such as 'pods, larvae etc. which can not only be detrivores, but can provide a food source for corals and fish. Trapping these in filter wool or some other form of mechanical filtration can lead to their death and eventual population decline.

The other issue with mechanical filtration is the trapping of organic material. This leads to breakdown of the material in the tank, leaking Ammonia, Phosphate, and other undesirables. This material could have been eaten by the aforementioned detrivores, rather than rotting in the tank, and the detrivores become a food source.

Regular (minimum weekly, if not daily) changes of the filter material reduce the impact of the latter issue to negligible. It's possible to recover some pods and other creatures from the filter material before disposal and potentially maintaining a healthy population of organisms in the tank and hence reducing the impact of the former issue. The question has to be asked by the reefer though, does the benefit of long term use outweigh the cost?

(Note - in the case of attempting to remove the various organisms from the filtration material, many of the organisms are not viewable to the naked eye, or well camouflaged. The existence of amphipods (see 'Pods) does not necessarily indicate a healthy population of the other organisms)