Green Mandarin and copepods with a 20 gallon tank with an in tank refugium.

So I plan on having a Green Mandarin with this tank of 20 gallons. The focus is not on what size your tank is, the size of the 20 gallon tank is to small or what can't be done. This is about it will be done and specs for it to be done. On an average how many copepods does a Green Mandarin eat in a day? How big of an in tank refugium will be needed to keep a strong copepods population. I plan on it being the primary food for the tank after it has been FULLY established with copepods for awhile. So don't go thinking I am not aware of their own going appetite for them throughout a day. My job is to have it always fed throughout each day. I want to know how long copepods take to mate, hatch, and be part of the tanks food source after they hatched? The in tank refugium will have a dry rock, black sand/crushed coral, and algea in it. The tank has 5lbs of live rock, 4 plastic plants decor, and the refugium when it is fully established. Yes I know 5lbs of live rock is going to be the biggest complaint. That is not what the focus is. So let's get sciencey and pick each other's brains. I know this makes me sound like a jerk saying the focal points, but we all know how much things get sidetracked.