I've seen this graph before and brought it up to the owner, but he is still adamant about aiming for 6, 6.3 being optimal.

According to that chart, there are both benefits to 5.5 and 6.3, but which direction is better?
immortal420 Reviewed by immortal420 on . ph, the "correct" range I've heard alot of stuff here and there, but I can never get a definite answer for this question. What should the ph be? I've heard 5.1 - 5.8, 5.2 being optimal. Local hydro shop owner says at those ph's, rockwool actually "melts??" Is this true? He's telling me to keep it 5.8 - 6.8, aiming for 6 and 6.3 being optimal. This is my problem. Rating: 5