Before adding any coral your SG
needs to come up to about 1.025.
Algae outbreaks usually indicate excess nutrients in the water. Can you post your actual readings from testing your water? pH, Ammonia, Nitrate, NitrIte, phosphate?
What kind of source water do you use when mixing new SW
for PWCs? How often are you doing PWCs? How often are you feeding, how much and what? What kind of filtration do you have on the tank? How much live rock do you have in the tank?