Flushing the media regularly is important for a couple of reasons. It keeps the nute levels from reaching toxic levels, which can be done with plain water, but is done better with Clearex. Also, Clearex unlocks nutrients that have precipitated into compounds that are unavailable to the plant, and those are again in a form the plant can use.

Botanicare says to flush weekly, and if you use a dense medium like rockwool slabs, it's a good idea. For growrocks, every 2-3 weeks is probably fine.

HTH

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