[thrillreefer]

A couple of generic suggestions. With any sandbed, it is important to keep it from getting compacted, but the best method is also the easiest: sand sifters. Adding some live sand periodically will help to replenish and diversify the small macroscopic sifters, like bristle worms and small brittle stars, etc. Sand sifting fish such as engineer gobies, watchmen and others can move a lot of sand, but with a DSB they may disturb anaerobic bottom layers more than is beneficial. There are plenty of others out there as well: tiger tail cucumbers, sand sifting stars (though there is some controversy over these), nassarius snails, and more. Try adding some of these to keep the sandbed a bit more open and reduce pockets where detritus and nitrates can build up.

The second suggestion is to make sure you don't have excess phosphate. Testing your tank can help, but often the phosphate is utilized by algae as soon as it becomes available, so the test will likely not reflect the amount of phosphate actually cycling in the tank. TEst the water you are getting from the store for phosphates (and silicates, if possible). They may even test it for you at the shop when you pick it up. Or you could get yourself an RODI unit. There are good ones for under $200. (I got mine at airwaterice.com) Then you can be sure that the filters are in good condition and be confident about make up water quality. The last thing to do is consider adding protein skimmer. In the Reef Aquarium Vol. 3 (Delbeek and Sprung), they cite a spectrographic test that shows that skimmate contains a sizeable proportion of phosphate. This is possibly because many lipids contain one or more phosphate groups at one end. Since the lipid is nonpolar and the phosphate group is polar/charged, these compounds are quite stable at the air/water interface on the surface of a bubble.

AS a last note, I've found that taking out afflicted rocks and scrubbing them clean with a stainless steel wire brush (rinse in a bucket of saltwater before returning to the tank) can really help to get algae under control. Sometimes you are doing everything to limit it's growth but it takes a round or two of physical removal to get it to the point where scavengers can keep it in check.

Also, though I've never tried it, some people report success with turning off the tank lights for 2-3 days to weaken or kill the algae. You could try searching for that method if you get desperate.