I have 2 hydra 26 HDs in a 85 gallon. I run them at 64watts which gives me about 140 par at the bottom. My ALK dipped from 11 to 7 over about 4 weeks. This is a new system so I just started to dose back up to 9dkh. I’m running 3-5 ppm nitrates and 460-480ppm calcium. I was dosing spectracide, Potassium Nitrate, to help color up my sps.