This ^^^ the sun hits my ATO water for at least 4 hours/day and I have 0 algae in there (I use a 10 gal fish tank for ato).Why do you think it's the light? Algae outbreaks are usually caused by excess nutrients, from feeding too much, or not doing water changes. Tell us a little more about your system. What do you have for livestock and what's your feeding/cleaning routines