Algae is partially caused by the excess light but high levels of po4
and/or excess nutrients are usually a greater problem. (read the Algae control
article for more info)
A good current at the surface induced with multiple power heads as roka mentioned is the best way to reduce possible co2
build up. Keeping your tank topless is important as well since glass tops trap co2
I've gathered from your other posts that you have a 14 gal
tank with two young clowns and have been feeding flake mostly.
Flake is notorious for not being eaten and contributing greatly to increasing your po4
levels which algae feed off. Frozen has much smaller quantities of po4
and I'd reduce the amount of feedings to what your two fish can consume within 2-3 minutes to limit excess waste (no3
Since the tank weight is around 50-70 lbs half empty I'd relocate the tank way from the window when you do your next pwc
or at the very least get some curtains.