I don’t know what else I can do! I’ve been struggling with this type of algae (or cyano idk what is this) for some months. I did several water changes in order to stop the development. I spend my weeks quiting the algae of the tank and scrubbing the rocks, idk what else I can do.
Several months is a quite a while to be living with this. Without seeing your plumbing, I would suggest adding chemicals which remove nitrate and phosphate, and assuming you have a sump and protein skimmer, check that they're not harboring any of this stuff in there as well. Also, use reverse osmosis filtered water to make up your salt water. Continue vacuuming the slime. I'm not sure aggressive water changes are beneficial. I would not use antibiotics, but I've heard "Chemiclean" is useful here.
Make sure no sunlight, direct or indirect is hitting the tank. Try to get some other bacteria going to outcompete the cyano by dosing microbacter 7 or equivalent.