k just setting up new 12 site ebb and grow system useing tap water in 55 gal drum for res my water out of tap reads approx 200ppm on a com-100 meter by hm digital. question is im starting seeds in rockwool feminized monster kush i took a gal of water and added less than quarter teaspoon of thrive alive my ppm jumped to 800 is this normal? i decided better safe than sorry so i flushed gal of water till ppm came down to 275 then i flushed rockwool cubes with solution and now have them in plastic dish bout 30 inches from 400 w hps { just useing to veg}
any advice would be appreciated i have chiller on way for res and right now res is full of just water

no that is not normal... 200ppm to 800ppm... how much water are you working with. You say a 55gal drum but how much water is in there.