Sand or mud in fuge

i feel that a sump or refugium is the single best thing you can add to a reef.i noticed an immediate change for the good as soon as i added a sump with live rock and chaetto in it.the bad hair algae slowly faded away till it slowly disapeared and the copods breed very well in the sump and get blown out into the display tank where their eatten.i tested the 1st perfect water test right after adding my sump and the return pump added extra flow in the displat tank.i add some carbon once in awhile to keep the water cleer and from smelling.i only need a 5 gallon per month water change and add i small amount of magnesium,it gets low idk why,now to keep my reef .