A skimmer is a device to clean impurities from the water surface, installed to reduce maintenance. A pump is causing a flow to an opening with a basket behind it, catching and filtering what comes with the water. Thus, impurities end up in the basket and not at the bottom of the pool.
Skimmers are known from conventional pools, they are very useful for catching leaves and other particles that float. In biologicals, wall-mounted skimmers are also used, but there are also round-shaped skimmers with a floating waist, on which the flow of water catches leaves and dust swimming on the surface. All skimmers need pumps. In the case of biological pools, the water is transported directly to the plant area or to an external biological filter, from where it returns by gravity to the plant area.
Undoubtedly, a skimmer needs some maintenance. Because without regular cleaning of the skimmer basket, where the trapped debris accumulates, this equipment turns from a help to a problem. Situations as shown in the photo are unacceptable because the dirt caught in the skimmer is already decomposing. Sure enough, this skimmer hasn’t been cleaned for weeks.
Alternatives to skimmer exist. For example, it is often possible to configure the biological pool in a way that prevailing winds push leaves and dust to a bay in the plants area where they are trapped between plants and accumulate in this place, foreseen in the project for this purpose. There, they are transformed from organic matter into nutrients, which in turn are incorporated into certain plant species placed in this bay and transformed into biomass.