What's that white stuff?
Seeing white stuff on the top of your LECA? So long as you rule out mold, don’t worry. It’s a reaction called efflorescence. Water evaporates, but the minerals in it do not. This leftover mineral deposit is what accumulates on your LECA. Think of the white build up that you commonly see on retaining walls and driveways. It’s the remnants of water that have been left behind over the years.
You can get rid of efflorescence easily by flushing the LECA. Using distilled or RO water in your nutrient solution will slow the buildup.