Help! Green Water?

[Jeff Coart <rapdfire at pacbell_net>]

I get very cloudy water by midday and then by day's end it's completely
gone. The cloudiness has a definite green tinge to it. Is this green
water? Why does it develop in the afternoon and then disappear by
evening?

I'm also getting some bright green algae on the glass that reappears in
a few hours after I wipe it off. Shows up on some plant leaves as well.
How do I get rid of it?

Tank parameters:

-50 gallon water column
-KH 5
-PH 6.4 - 6.7
-NO3 5-10 ppm
-165 watts CF

Tank is 18 months old; heavily planted.
Dose K2SO4 at 1/2 tsp after weekly 50% water change plus a few drops
phosphate (via fleet enema) 1/4 tsp KNO3 (plus additional as necessary
during the week) and 3-4 ml traces. DIY CO2 which I change weekly.

My plants are growing well and are all healthy. Thanks.