9/26/2012 4:09 AM
Spike or Aerify the area to open up the soil surface, get air in the sandy soil, moisture in, and dry out the algae. You could leave it open for a little while and dry it down, then topdress with good mixture. May need to even do it a couple of times to open the site back up if it is really sealed up. If it is a small site also a hand spiker can be of good use to release the surface algae and help set seed into sand, then a little topdressing. JMO...Good Luck
Gregg R.