Hi,
Wow that's some beautiful rock pieces, but I think you need more rock... Cyanobacteria is caused from too many nutrients that are settling on the sand. You either need to not feed as much food so it isn't wasted and/or have more water flow so the stuff doesn't settle on the sand. You don't have to get a sand sifter goby, nassarius snails for example stir the sand as well. In a new tank, the brown algae will be on everything and go away on it's own, it's a normal stage