Algae, Algae and more algae

[jjhill]

So in my tank right now I have green hair algae, not a lot there is a light green color to most of the rocks and the back smokescreen of the tank is quite hairy. I also have very small amounts of red cynobacteria. But the real kicker is the tank is full of brown diatoms. The sand is almost all brown. There is a brown dusting on all the rocks, and even the green hair algae has been turning brown.

The tank is new about 2.5 months since cycling was complete so some of this may be accounted by a new tank. The phosphate levels, ammonia levels, nitrite and nitrate levels are all undetectable. I know this may be because the algae is using them up making them appear to be low when in reality they may not be, although even when I have done a water change, siphoned as much algae as possible, cleaned all the rocks and the glass and tested again I still can not detect any chemistry problems.

I use only R/O water for water changes and top offs, so I am at a loss to explain and get rid of all this algae. I thought it may be the lights so I cut the lighting back to only 8 hours a day but have not seen any improvements. Any suggestions from anyone? This algae is really getting annoying.