My RubberMaid sump. It contains probes, heaters, skimmer and it's pump. The skimmer is a downdraft type purchased from Premium Aquatics. It is an ETS knock-off and works very well. Currently powered by a Mag 7 but soon to be changed to a Sen. I am a big believer in using protein skimming and I have used the technique for many years. My first skimmer was a little in-tank Sanders unit on my first reef tank (a 30 gallon) in about 1985. Since then, I have used many different skimmers, from the infamous Skilter to 5 foot tall DYI  air-driven units to this downdraft. I have spoken to several people who advocate using no skimmer at all, but when I pin them down, most admit that they use a skimmer for a few hours a day or at night. I am not saying a skimmerless tank would NOT work, it's just that a skimmer seems to work well for me.