Nothing. Que Sera Sera. If you put a lid on it and block the light, the algea won't grow in other chambers. It depends on where you place the macro, put it after the skimmer section and it will clogg on the sponges.
I have an acrylic lid over the tank and the section, 2nd after filter socks, is see through/clear. I painted over the other sections to reduce/inhibit light entering the tank. See my build thread for more info