With a bypass from the aquarium main pump or with an extra pump the feed water arrives to the system. The water flow is adjusted in that way, that the complete filter material is in motion.
Phosphate and silica are removed from the water flowing along the filter material. The out-coming and phosphate-reduced water flows back to the aquarium.
If the phosphate concentration exceeds the wished maximum concentration you have to change the filter materia.
If you have aquaria with different phosphate wishes (e.g. hard coral tank with 0.05 mg/l and a fish tank with 0.5 mg/l) use the filter material first in the hard coral tank. If the wished concentration of 0.05 mg/l is reached take out the material und put it into the filter of the fish system.