Your friend is wrong.
As for the PH. you are going to be battling that with whatever setup or nutrients you use.
You will need a PH buffer. Biobizz - is a decent 1. You can go without 1 but you are going to have to change water continuously. As your plant takes up water it leaves some behind, (nutrients) if you have added to much. The buffers in the nutrient mix make it jump up as there's less water and so on. Well, that's my take on it anyways.
It doesn't gel together with other nutrients.