You should check your "nutrient" water parameters. (Phosphate, Nitrate, Nitrite, Ammonia)
A few things that help control cyanobacteria:
Nutrient Export:
1. Decent skimming
2. Filter
sock (changed every 2-3 days)
3. Phosban Reactor (Media changed regularly)
4. Activated Carbon
5. Regular (small) water changes
6. Dont add excessive nutrients to begin with. Fish do not need to eat nearly as much as people think. (Except for Anthias)
Other Areas:
1. Water flow. Good return pump and a well placed powerhead or two will keep the ditritus and other nutrients suspended long enough to reach the overflow, filter sock and skimmer.
2. Good calcium suplementation (High calcium and alk levels combined with low phosphates encourage coraline algae growth that will compete with cyanobacteria in a healthy system)
3. Ditritivores. Get a sea cucumber, brittle stars, hermit crabs and other critters that keep things moving around in the sand, on the rocks and in the crevices.
-Alfred
