If your using tap water that should be the total of tap+nutrient. Those ppms in your tap are nutrients too, mostly calcium. go with the 500 ppm and watch for nute burn, though I doubt you'll see any at that level.
I have a HM Digital AP-1 TDS and a PH-80.
Questions:
When using Megacrop ya keep the ppm to 400-500ppm. Is that added ppm or total ppm.......ppm of the water plus Megacrop.
Should I check the Ph after adding the Megacrop?
Or after getting into a routine, ph the water down slightly before adding the Megacrop, check the ppm add theMegacrop and then ph check the ending result to stay in that ppm range after? That's assuming the 400-500ppm is the added ppm and not total ppm.
Thanks for your valued input.