Carbon or no carbon?

[Imlovinit]

I have a 29gallon nano cube. Have had it up and running for a few months now. The system itself is pretty much how it was purchased...... As a plug and play with no add-on's yet other than a skimmer. We had originally set it up as instructed with the bio balls, foam, and carbon.......after talking with LFS we were advised to remove the carbon as it would be removing nutrients...... I have noticed lately that our water does not seem to be as clear as it was. Should I replace carbon? We feed our corals with photo plankton twice a week and supplement with Kent marine coral vite once a week....... Any advice would help.