I have neither skimmer, nor sump and I do a 15-20% water change on my 125g reef and 55g aggressive every 4-6 weeks. I have no issues with trates, trites or any other water problem. I have 130+/- lbs of lr and a 4" dsb in my 125g tank and a bare glass floor in my aggressive. I keep the lights on in my 125g tank 16 hours a day and have NO algae problems. My filtration is 1 Fluval 404 canister, which I clean 1x/mo and a 350 gph Skilter, with the skimmer off-cause I don't need it. The 55g has a 400 gph hob filter and a 300 gph internal filter. I pick up all uneaten food from the floor of the tank and have 0 water issues. I am fastidious about water-monitering every 2 weeks, more if something doesn't look/feel right. In the last 3 1/2 years in SW, I spent too much money on an expensive sump and skimmer. I have had no problems with water quality without them.