I go skimmerless on my 29. But I do 5 gallon water changes per week so with liverock/sand/gravel removed probably 20 gallons of water left so thats 25% water changes. I can't do that on a 300. I have had in the past a 75 and a 158 where I only ran a skimmer one week out of the month because the skimmer did not skim otherwise. Both tanks had large amounts of Xenia and GSP which did a great job of filtering out impurities. As a matter of fact if i ran my skimmer too much my Xenia woulld quit pulsing. On my old 200 I had Xenia and GSP and still dumped the skimmer cup twice a week. I think we sometimes have a tendency to maybe run too large of a skimmer, but in most cases we still need to skim if only sometimes, unless we are replacing a lot of water in our tanks.