pappy when i run hydro, depending on the strain in veg I'm at around an EC of 2.0 and as i ramp up in flower i get to around an EC of 2.8 thats around week 4-5 and i hold that till i taper down around week seven to an EC of 1.5 then lastly to just water in weeks 8-9 as I let the plants use the last little bit of themselves up. Here is an EC conversion table, dunno if your TDS meter is a .5 or .7 thats why i stick to EC when doing hydro.