Bio-filtration: Is it enough?

I have a 45 gallon tank that has 50 lbs of live rock and one inch of live sand. I am also running two powerheads. I had read that bio filtration with the sand and rock combined with the current created by the powerheads is really all of the filtration that you need. I visited a new LFS today to purchase some ATI bulbs and the gentleman working looked almost offended do when I told him that I didn't plan on putting a skimmer on the tank. He told me that I was making my life way more stressfull than it needed to be and that I would end up doing 50% water changes every week because the water would be so unstable. He not only suggested that I put a skimmer on the tank but also a regular carbon filter as well. I feel like as long as I do regular small water changes I should be ok- what do you think?



I have read that carbon like filters can often times do more harm than good because they can hold on to bacteria and just infect your tank worse.