Welcome.
When I see threads like this I have to ask what are you trying to accomplish. Cheato should be self regulating, It's usually used as a nutrient export. Nutrients are high, the cheato grows fast, low and it stops. Today's tanks can be low to no nutrients. Skimmers and ATS can remove NO3/PO4 very quickly as will a mature tank stocked with corals out-competing the Cheato.
Thus members start to increase the nutrients to get the cheato to grow which makes no sense since they were seeking to remove nutrients and shifted focus on growing algae. ???
Before anyone can help you, start with posting your NO3/PO4 numbers and what test kits are being used. Also what lights (although I grow forests of the stuff with cheap plant LEDs).