What would be the best sand sifter or a 14 gallon nano?

When I had a slime algae outbreak, my trusted LFS owner said to lower light time and vacuum the sand once a week. Is vacuuming sand in a reef tank needed or benificial like a skimmer? If I have a sand sifting goby, do I still need to vacuum? Now my sand is turning a brown color, like it's...