If you want to encourage algae growth then do the following: turn off the skimmer, feed your fish daily and overfeed them as well, use conditioned tap water for top offs, and make sure that the tank gets some direct sunlight during the day. My tank gets sunlight reflected off of a window during the late afternoon, and every surface that the light hits has huge flowing growths of hair algae.
Childawg, I didn't even think about the currency conversion, good point. Anyway Adam, tangs can be picky eaters. You might try getting some of the dried seaweed I mentioned earlier. My tang LOVED that stuff.