Strong flow will also not allow Cyanobacteria to form, it likes nice calm areas. I think weekly water changes, watching how long your tank lights are on and a proper feeding regiment will cure your problems without use of additional chemicals. But Polysorb and Chemipure can help if there is no natural way to get organic levels down. Cyanobacteria can grow in tanks with very low organic levels, there is thought that says selenium, that is in some salts and some sand can cause it to grow. In my tank, it can start where there isn't any current at all. Like in a corner.