The water you use for your plants will determine how well your plants will grow, regardless of what you add in terms of nutrients and supplements. PPM (parts per million) or EC (electrical conductivity) are the meaurements of the salts in a solution. Neither PPM nor EC readings will tell you what is in your solution / water, but rather are indicators of the solutions ability to conduct electricity. Ideally, you want to start off with a low PPM or EC then you can add nutrients specific to your plants requirements. If your water / solution has a high PPM or EC, it can be reduced using a Reverse Osmosis (R.O.) unit then build your nutrient solution around what your plants need.