If you lower the water level enough so that the filter outflow creates some splash, punch, that may be enough. Various oxidizers have been used to counter cyanobacteria: potassium permanganate, hydrogen peroxide. Lowering dissolved organics and encouraging plants to photosynthesize both raise O2 levels in the water.
(Cyanobacteria invented the kind of photosynthesis that produced oxygen (a while back). For them, O2 is waste. Too much oxygen represses cyanobacteria. That's the theory anyway.)
Your "photoperiod" setting on your light timer shouldn't be longer than nine hours for now. Cyanobacteria have no diurnal clock to stop them: they keep on going, unlike algae and plants. Long "lit" hours favor cyanobacteria without benefiting plants. --That's shorter hours, not less light.
And keep siphoning the stuff up, as HazyWater and others have suggested.
(Cyanobacteria invented the kind of photosynthesis that produced oxygen (a while back). For them, O2 is waste. Too much oxygen represses cyanobacteria. That's the theory anyway.)
Your "photoperiod" setting on your light timer shouldn't be longer than nine hours for now. Cyanobacteria have no diurnal clock to stop them: they keep on going, unlike algae and plants. Long "lit" hours favor cyanobacteria without benefiting plants. --That's shorter hours, not less light.
And keep siphoning the stuff up, as HazyWater and others have suggested.