Would sand or mud get sucked up into the return pump? Can would the detrius really be cleaned up be the snails or would they just be hidden in the sand?
As for the sump, I originally had a piece of glass where the eggcrate was, but my original pump (Mag5) and my second pump (Sicce Silence) resonated with the glass there. I decided to pull it out and it got a lot better. Then I switched to Eheim and it was even better. I may put the glass back, but then I wouldn't have a refugium for a couple of days.