During heavy pulse recirculation an air pump is turned on diffusing air near the pumps inlet for 2 – (1 minute) periods. The air injection floods the tank with fine bubbles for a few minutes. The bubbles attach to floating waste particles and assist in floating out the waste and exporting it to the over flow weir. The fine bubbles also causes the SPS coral to release a lot of slime as the bubbles attach to it and floating it off.
Taken From here
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