ph for my plants

I think you should always stay in the 6.5 to 7.0 range no matter how big the plants are

i thought 65-7 was to high for rockwoll, iv'e got rain watter in the one wilma ,the ph is bang on 7 .but iv'e @ to use tap watter in the other willma tray i need to no what the the best !!! don't wont 2 go under or over the limit.