Yeah I think I may have misread it, my dad has a saltwater tank and at 40 ppm that's when fish die, but my lfs store owner who has a degree in being a vet and who has bred various fish has said it's only at 200 ppm most fish begin to die. I think I'm doing fine since none of my fish are dead or showing signs of illness and my peacock gudgeons are showing signs of being ready to breed. Thanks for the good luck and for your input