The brown algae is probably diatom resulting from the phosphate in the water. It's also present during a new tank cycling in. Don't buy distilled water at the store. Use RO/DI instead. If you don't have access to RO/DI, buy the RO water from the dispensing machine w/ the picture of the Penguin. After your tank is stable, get some snails to clean out the diatom. You can dose Kalkwasser to precipatate the phosphate out of solution. When you get your RO/DI unit in, do some big water change. Try to replace the filter pads in your RO/DI everything six month.