I have been running my 40 gallon system with fish and corals for over a year without using a skimmer, just a very aggressive algae turf scrubber and have no detectable phosphate or nitrate. I do monthly water changes and other than mechanical disasters (hurricane sandy,, etc) everyone seems fine in the tank. OTOH, I do run a skimmer on my 220 FOWLR as well as an algae scrubber, and that tank is doing well too. You pays your money (invariably, lots of it) and you takes your choice. I think either system can work well.