Dont know about hydro but for soil the ph should be between 6.3 and 6.8....not all destiled water has a neutral 7.0 ph (the one i buy has 5.8)..so just by a 5$ ph test kit and some ph+ and ph- solutions (u can get them real cheap)....although i´ve read a thread recently by Garden Knowm in wich some seeds were grown with 8.0ph water, but in this particular case Miracle Grow was also used....so test the water and make sure the ph readings are within the mentioned levels...happy gowing dude...