What are the optimum water chemistry parameters for the ionization in water features?

The optimum water chemistry parameters are: Copper:  0.25 mg/L (ppm) or less; Total Alkalinity: 100 - 250 mg/L (ppm); and PH:  7.2 - 7.8 (ideal but can vary). The farther away your water parameters are from these optimum levels, the less effective ionization will be at treating the water.  It should also be noted that Copper levels above 0.25 mg/L (ppm) may be toxic to fish.