I thought scuds and PK shrimp were mostly detritus eaters plus perhaps some tiny zooplankton they could catch. Do they feed and denude vegetation in ponds?
If so, and you are worried about adding them, I think most pond owners might be able to drain down their pond down 3-5' such that the scuds and/or shrimp have very little protection from predators?
However, I don't think that would work for large watershed pond owners like catscratch that cannot pull down their water levels.
I thought the decision on scuds/shrimp was that they might establish in the pond, or they fail to establish and you wasted your time and money? Is there also a decision that needs to be evaluated that these crustaceans can be an actual detriment to a pond?