I've seen precipitation form when the liquid runs down the side of the sump and dries before going into the water like @Terence tank did. Can't remember how he remedied the situation. However, are you talking about precipitation forming after the liquid is in the sump water, on the bottom of the sump in a slurry?I have been struggling to find a dosing pattern and location in the sump that doesn't create precipitation. Can you please tell me where the magical place in my sump is where water passes through at a high flow rate so to avoid precipitation? If it isn't in the return chamber, skimmer chamber, or refugium...then where is it?