I have never had this much trouble growing coraline algae. My 39g just refuses. Ive recently started dosiing 2 part everyday 2 weeks ago. My display will not grow it, but my fuge under a low wattage florescent bulb is growing it now at a good rate of speed. What gives why will it grow in my fuge but not the display under the MH. Same water so the only thing that makes since is the lighting. Maybe the color spectrum differnce??