As
@LexLuthor said, your biggest concern for dealing with algae is light elimination. Especially if you're using rockwool blocks, covering the tops from light exposure will have significantly higher benefits than any additives as algae requires light to grow.
I use 3ml/gallon of 29% food grade h2o2 in my res. Apply every three days. I also use
hygrozyme in conjunction with h2o2. Be cautious of using 3% h2o2 bought at a pharmacy or grocery store as it is stabilized h2o2, and while it will work in a pinch, it has additional chemicals in it that might have negative interactions with other molecules in your nutrient solution. Best to use food grade h2o2 since it's not stabilized. Just be careful with the stuff. Wear eye protections and chemical-resistant gloves as it is a pretty aggressive oxidizer.