there should be countless threads and advice on how to do it, but the short of it is:
check your water params,
you want zero ammo, zero nitrite, and as close to zero nitrate as possible
-fix with refugium, less feedings or less food at feedings, LS instead of CC bed, water changes
what is your PO4 at? you want as little phosphate as possible
- fix with refugium, less food, better food (less frozen cubes), water changes
more overall flow inside the tank
smaller photoperiod