It can't be in the same area as your fuge, because you NEED a UV sterilizer downstream from the aiptasia farm to kill any aiptasia spores or pieces that can travel in your water to the main tank. You do not want aiptasia in your main tank and using a UV sterilizer will help prevent that. If you do not use a UV sterilizer after the aiptasia farm, it's pretty much a guarantee that your main tank will get infested.
If you have the aiptasia and fuge in the same place and have a UV sterilizer downstream from it, the UV will kill all your pods and live food that you are trying to produce in the fuge. It will defeat the purpose of having a refuge for live food in the first place.
I don't know why someone would choose aiptasia over xenia either, if they were going to have something in the fuge. What a pain in the ass to maintain.
Xenia would not have to be kept separate because they are not as much of a risk of spreading to the main tank.