How much sand do you lose when siphoning your tank

[AtlanticGail]

When siphoning my tanks sand I notice everytime I vacuum the sand I end up loosing some. Also when vacuuming up cyano from sand bed I notice much of the cyano just falls back onto the sand rather then getting siphon .

 

[Dan_P]

When siphoning my tanks sand I notice everytime I vacuum the sand I end up loosing some. Also when vacuuming up cyano from sand bed I notice much of the cyano just falls back onto the sand rather then getting siphon .

Add fresh sand to make up for the loss.