Try gently netting it with a coarse net which would allow the
sand to go through, but still catch the soil pieces. You might have to make a temp homemade net using onion bag netting or even some piece of
media bag material that is with openings just big enough to grab the soil chunks carefully and still allow the sand to go through. You also could try a turkey baster if done carefully. You don’t want to obliterate the soil pieces. You might get some sand with each baster use, but you can remove the sand later on.
Btw…..your pic looks fine. I did not think, when I saw it, that the soil pieces detracted from the pic. But….I do understand your desire to clean it up a bit. I’d probably try to do the same.