220 feet of it with a 30lb stress rating. Will be purchasing tiny metal mooring connectors tomorrow that will allow the habitat to rotate in the wind without twisting the line.
The solution is to have the habitat hanging independently on its own line. Even if the balloon is directly overhead, provided a long enough line the habitat should hang more or less level. And assuming it is always at (at least a slight) angle from the weight holding the line down, this solution is much better and will keep the habitat level regardless of the balloon's movement.