After realising the problem, I stopped adding CaCl2, KH slowly climbed back to around 7, macroalgae started to grow, and coraline algae grew a lot slower. I have been researching corallines recently. A lot of references can be found concerning speciation classifications, but I have been unable to find many articles detailing metabolisms. Have just started search though. I have yet to find data observed for a specific corallinaceae.
Nitrates are nutrients for red algae which can limit growth if too low.
They are also toxic if too high. More research needed to confirm this. That which applies to calcificating coral- line, might also apply to sceleractinian corals. The other possible growth war inducer, might be the potential calcification rate. If both are true, a reef which supports heavy green algae growth, might not support good calcification or coralline growth.