PPM (Parts Per Million) is the unit of measurement your using to measure the TDS (Total Disolved Solids) of your water, feed, etc. So to increase your PPM you need to add more disolved solids into your feed. Disolved solids would be your nutrients your using. PH up and down also affect your PPM so make sure and take that into consideration. You just have to play with your nute lineup and figure out your butter zone for your plants and the total PPM your looking to achieve. Hope that helps, TWB