The water is filtered then treated..The bulbs are just the ones that came with the tank. There is green algea on the rocks also but only the brown on the glass bothers me. Tank was 2 yrs. old and established, then my fish guy went on vacation and the new guy told me my bed was too deep and i should take some live sand out. Well,you all know what happened...Nitrates thru the roof and everything died. so we waited for it to cycle again, when everthing went to 0(ph was low so i added buffer)brought it up to 8.1 ; waited a week and got cheap,expendable fish. It had not had fish or food in the tank for months,(waiting on cycle)just got fish last week. For everyone who is cussing the store,they replaced the new guy and are making it right with me. Now,how about the brown diatoms,since you know the rest of the story. i don't remember having this problem before,should i go back to buying distilled water to add when it evaporates down? I have never changed water more than every 3 months or so and then, just 20%. the tank sorta takes care of itself. until i removed sand this was a happy tank with 10lbs live rock,live sand, and 6 fishies.