Lifters making noise. Should I put special oil?

I noticed some noise under the hood of my car: https://youtu.be/E7o1uhSYOJY

I had my mechanic see my car today and he said that the lifters inside the engine are making noise. He suggested two things:

  1. Buy a special type of lifter liquid to put inside with the engine oil to help the lifters from making noise.

  2. Replace the oil pump (not quite sure what he meant).

Can that special liquid fix one thing but damage another? Is it recommended? If the problem is with lifters, do I /need/ to fix it if the sound does not bother me?

Thanks all!