DIY CO2 is unlikely to overdose CO2, so I suggest not trying to get rid of any at night. If you do want to cut it back at night an air stone is the usual method. Most algae will not be killed by adding CO2 - algae love CO2 as much as plants do. So, you have to get rid of the algae first using mechanical means or removing and dipping everything in bleach solution, or using hydrogen peroxide. If one of the algae is green dust algae, on the glass, you almost have to let it grow thru its life cycle, which takes about 3 weeks, without disturbing it at all, then wiping it off the glass. For the other types, once you have removed all of it, started dosing ferts consistently and adequately, gotten your CO2 ppm up to an adequate amount, you should not see any more algae start up. What little you do see, if you immediately remove it, you should be almost algae free.