hmm just to be safe, i'm going to cover the tank window faced with a trash bag that i just bought. hopefully that's enough to slow down algae growth. i just finished my blackout treatment and i managed to clean over 90% of the algae on my tank hahahaIt’s hard to know without knowing what kind of light that is. But I would think the window/door near the tank would be the cause of ambient light issues since natural light is much stronger. I have some ambient light as well that hits the tank about an hour a day, and I use a curtain to diffuse it a little. Then I fine tuned my aquarium light amount until I hit a balance that didn’t cause too much algae. Of course algae could be caused by other issues besides too much light, but that’s another conversation.