i setup my 20 gal about a month ago and I have this setup:
Tunze protein skimmer- love this thing. I started with coralife one and I hated it.
20# live rock
5# live sand
Just added a nano powerhead today and it seems like the perfect flow rate for this tank
lights are the cheapos that came with the tank- no plan to do corals or anemone until the tank is well established
I used a product called stablize to help the tank to cycle. It was ready for the cleanup crew after a week. Next I added two clownfish, a cleaner shrimp and starfish. My levels have been steady and I change about 10% of the water every two weeks.