Reducing the photoperiod doesn't deal with the underlying problem that causes these things. The increase in light merely allowed what was already there the extra "umf" to get it going. The main concerns are nutrient and phopsphorous. Get those under control/eliminated and the algae will abate. Sounds simple but for the most part it is. It's just a bit time consuming and generally requires a fair amount of effort on the hobbyists part. There are no real quick fix's that will be permanent. Increased water changes with RO
, removing the algae by hand, reduced feeding, examining the health of the bioload vs the tanks ability to deal with it, the effctiveness and quality of the water flow, draining the phosphates from foods before use, types of foods used and reducing P as much as possible from the tank.
As far as the sand is concerned, just replace what gets removed. It's most likely just the surface area's anyway. Adding cerith and nassarius snails (water quality depending) are a good way of helping the sandbed stay healthy and clean.