Robin,
You can take his advice or ours. They are contradictory. You cannot follow both.

You may or may not believe me, but his advice is good for one thing--ringing up the register. It is NOT good advice for your pool.

He's telling you to increase hardness in a vinyl pool. This is pure utter nonsense. The reason is that the "hardness" is calcium and calcium is needed to prevent the water from leaching calcium from the concrete or plaster walls. There's no calcium to leach from vinyl so it's pure garbage.

As I said, you can follow his advice or ours, but if you follow his and it doesn't work, it's that much harder for us to help you.