Derek
The link in the bottow of my post is a good post with tons of information. About 4 posts down in the below link Bill Cody has a bunch of links for you. Scuds are small invertebrates that are a favorite forage source for smaller fish but also in themselves do good things to help break down your debris.
They usually are considered a big group in the Gammarus Genus and have many common names. Some pondmeisters are lucky to have ponds teeming with them naturally and some web sites sell them to lovers of ducks for them to stock in their wetlands as ducks love to forage in the leaves and eat them.
Scuds 
