Why do my plants only pearl when I do a 20 percent water change. I have pressurized co2 system. I have 2 bubbles per second going in the bubble counter and which gets diffused into the aquarium with a reactor 500 from Red Sea. My ph starts out in the morning at 7.1 and goes down to 6.7 with the addition of the co2 daily. I also have a constant 3 dkh of kh. I have a ph controller that shuts off the co2 once it gets to 6.7. So shouldnt my plants pearl with the co2 I am putting in my tank alone? Please help...!!