Algae turning white

[FragIt Dan]

Possible your algae has gone reproductive. Many algae have several life stages, so it may have just move from one to another. Given no other significant changes I would say this is likely what has happened and have seen it happen in my tank years ago. There would be many possible reasons for it doing so, none of which would concern me were it my tank. You might want to do a water change just as an opportunity to get some if that biological material out of the tank while it is suspended in the water column or sluffing off your rocks. Alternatively you may get a bit of nitrate build up as it decays.