Well, you may want to encourage diatom growth as they are an awesome food source for filter feeders (many corals, clams, sea cucumbers, etc.) as well as being food for your live sand. I dose silica to maintain 1ppm in my tank just to encourage their growth.
One immediate benefit was that the glass was easier to clean. The mix of both blue-green algae and diatoms that grows on my glass now is markedly easier to remove than blue-green algae. Second, nitrates are about half the levels they were before I started dosing silica (diatoms consume dissolved nutrients and many are skimmed out). Phosphate has never been an issue in my tank (sometimes measures at 1ppm) so no real changes there. As for the benefits to my filter feeders, I don't feed as often as I used to, but the corals are growing even faster than before. Not a reliable experiment, I know, but they're getting nutrition from somewhere to be growing as fast as they do.
Far from being irritated or frustrated about a patch of diatoms on your sand, I'd be thrilled. They're an important part of the natural food chain and if you can keep the diatom populations at a sustainable level (below the bloom level), I think you'll be very happy about the positive effects on your tank.
Regards,
Ross