I am at opposites with Niko on this.. I would think that a skimmer would be more beneficial in a fish only and less with live rock, as you don't have the diversity of organisms in fish only. However, with starters out, I must recommend a skimmer, as it creates a much needed buffer for the unforeseen. And we all want to reduce the over all damage if anything goes wrong, that is where over filtration can help. But Niko knows where I am coming from ; ). Also, with that size of water volume, you have a very high inbuilt stability...... Oh, I still haven't done that water change.