I have three in with 3 black skirts and 4 ADF. They pretty much leave the adf's alone, but they reserve all there hostility for the tetra's even tho they are more than twice there size.
Abercrombie- I think it might have something to do with the fact that the shimp you have in with yours stay mainly on the bottom, like I said, mine done even act like the frogs exsist, but they stay almost always on the bottom. Doesnt fully make since, because my puffers swin in all areas of the tank, but hey, Im not knockin it!