vinegar till PH went to 6.0

[Lee]

Dear Hydro, I started my water out at 6.0 PH, then added nutrient, Miracle Grow. The solution went to 7.0 PH. Then I adjusted it down to 6.0 with vinegar. After several hours and several floods, the PH went back to 7.0. After 48 hrs. I adjusted once again with vinegar till PH went to 6.0. The PH is still fluctuates, always heading toward the alkaline side. What's wrong? Mom's fish water does that same thing. Got any suggestions, would appreciate your input greatly. Lee

[Ron]

Miracle Grow is naturally alkaline.
I would try a different pH down than vinegar. That fish store pH down works OK.