The only way I can see that the circulation pump would get sand into your overflow is if the fish are stirring up the sand enough that it becomes suspended in the water column.
The only way I can see that the circulation pump would get sand into your overflow is if the fish are stirring up the sand enough that it becomes suspended in the water column.
+1. I have a 1500 gph Korallia about 6" from the bottom and another on the opposite side about 10" from the bottom without issue. Although I could of seen it being an issue before I switched to pool filter sand from play sand. Play sand would get everywhere.