I'm going to have to say penalty on this one. I don't have a specific rule to back it up, but here's a reason for my call: The rule that you have to leave the loading zone before getting another tetra only works if you entered the zone in the first place. I believe that actions should be called consistently, so if you allow a "tetra nock" to legally get a tetra from the loading station, you've allowed the teams to circumvent the rule.
--EDIT--
Sorry if this repeats something someone else has said. I started it this morning, but then I had to go to school...
