Four weeks ago I started an observation hive with 4 medium frames. To begin with it had bees thickly covering 2 full frames and part of a third, but now through attrition there aren't enough bees left to cover both sides of 1 frame. There are swaths of capped brood on each side of that frame, and the first few new workers have just begun to hatch out. Even so, I don't think there will be enough bees in the short term, and certainly not enough foragers.

If I want to boost the population, should I:

- add a frame or two of capped brood from another hive?
- add frame(s) of capped brood with nurse bees on them? Would they be accepted, and would they accept the queen?
- transfer the bees into a nuc to try and let them build up in a less stressful environment before putting them back in the observation hive?
- something else?