Mysis Relicta

[Peregrine]

I don't do it often, its more of a treat, but mine have trouble catching them. They close in slowly, the shrimp flinches..and everyone freaks out and retreats. They will repeat this a few times, and more often than not the oldest one comes to the surface and waits for me to feed him by hand, leaving the younger one to chase the food around the tank

Word to the wise, however, if you do put live shrimp in an aggressive puffer tank..make sure the lid is closed right after...the little buggars (shrimp) can jump clean outta the water, and travel a considerable distance
And until they tire themselves out, they can be hard to catch...like catching grass hoppers, always jumping just before you have them.

[Phaedrus]

Lots of little caves, nooks, and/or crannies are a must to help keep them from freaking out. They also seem to do this alot more often in smaller tanks than larger. They also seem to settle in after a week or so given enough hiding places.

[Peregrine]

The F8's tank is heavily decorated with plants, mangrove roots and large rocks (all synthetic)
I think they are just reacting to a fast moving new addition to the tank (even if it is food)
most of the food they get does not try to get away

As for the shrimp..cant blame them for freaking out
If I was on the menu, in unfamiliar surroundings I would be jumpy too
They are normally kept in a FW community tank (55 gal)..where they behave dramatically different