they seem to clear up at night and populate during the day. Any thoughts??
The algae is producing oxygen during the day when the lights are on, during the night they are not and the bubbles have a chance to dissipate.
The best way to deal with cyanobacteria, is to have good waterflow, use RO
water for top offs and waterchanges. Siphon it out when doing waterchanges. Make sure you have good waterflow through out the tank and good lighting with plenty of actinic spectrum. If you use a skimmer make sure it is running efficiently, if you don't use one...you may want to increase the water changes for nutrient removal.