My 30 gallon got so bad that a couple days ago I took every coral and piece of rock out of it, and skimmed the top 1/8" of sand off the top to throw away... I had considered a sand sifting star, but heard about them eating the good stuff as well as the bad, and then starving.
I did by a hairy sea hare thinking he would solve the problem, but he only wants to eat algae from the rocks and glass, nothing at all from the sand. If it ever gets really bad in my tank again, maybe a cucumber would be my best bet.