I don't think I've ever cycled a tank and not had brown diatoms in the tank. Normally they appear as the tank cycles and then are replaced with green algae. You can avoid most of this by having a large cleaner crew. Different snails eat different types of algae along with hermits that tend to stir the gravel helping to prevent algae from getting a hold there. My 210 has hundreds of snails, hermits, and a few mithrax crabs, hundreds of pods, and several urchins. Reefs don't stay free of algae just because of the nutrient poor water alone. There are thousands of creatures that eat the algae and the trick is to find the ones that make a good addition to your tank.