What kinda system ?
Algae never bothers me . In my sys. it's only ever on the lil rockwool starter cube , and once plants are big enough to block light from the cubes the algae dies from no light . If it really bugs ya I have used a 1/2 a tsp. of 3 % h2o2 per gallon of water in the given system and it'll kill it .
Peace
Crispi :jointsmile: