Blue-green algae and water movement

I've had BG algae reappear twice in my 180 during the last year.
In each case I cut back the plant stems that had clogged the
surface preventing water movement and light below. I turned on
a powerhead and added extra CO2 and other nutrients. The change
in conditions caused the plague to disappear. This is mentionned
in Aquarium Plants by Rataj, pp. 51 and 54. He states that
water movement and a change in light intensity up or down will
discourage this algae. I read in some academic text that it 
generally does not reproduce well where oxygen levels are high
which might explain the above.

Dave Whittaker                       ac554 at FreeNet_Carleton.CA
Gloucester, Ontario                  dwhitt at magmacom_com