IMO, cyano is really hard to manually remove. If you don't remove it "all", the small/tiny pieces that are left in the tank will multiply rapidly by the seconds when the light is on. The only thing helped me removed all my cyano was blacking out. I tried more water movement, 0 PO4, 6 hours light period (only took cyano 2 hours to expand from a .25in piece to a 5in patch on the sand bed) and nothing really worked. I think you have to get rid of it first before trying to maintain a cyano-free tank and "any" amount of light will keep it alive.
Your corals will do fine for up to 4 or 5 days, IME. Out there, reefs get all kind of bad weather and corals don't get light for maybe a few weeks.
HTH