The built-in circulation pump generates a strong circulation current (upstream), that lowers the danger of blocking and channelling. A higher reaction rate is the consequence.
The in-coming water is de-oxygenated by the biological activity of the filter bacteria. If any or low oxygen is in the water the bacteria switch over to nitrate respiration and consume nitrate instead of oxygen; these bacteria obtain the required energy from the sulphur granulate. This de-nitrification process lowers the nitrate concentration of the water.
The out-coming water flows back to the aquarium with less nitrate. The outlet water must not be directed into filters with phosphate adsorbers.
As the sulphur granulate is used up over time, the material has to be refilled every few months. If the capacity of the filter is too high, part of the filter material can be removed from the filter (please store the removed material in a dry place).
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