They'll eat algae, algae wafers, flake food, catfish pellets - basically anything they can get hold of. They'll eat any dead fish/shrimp (although you should take dead fish/shrimp out of the tank so you don't foul the water or spread disease). They'll also eat vegetables, frozen food and proper shrimp food. The list goes on.
I feed all my shrimp Hikari Crab Bites and give blanched spinach and zucchini as a treat. They all have nice shiny shells and the females constantly have eggs.
Well, what I do with mine is pour boiling water over them when I'm making a cup of tea; by the time the tea's made, the peas are done enough
Then take the shells off; I'd crush them a bit for the shrimp; just between your fingers.
Had a goldfish die recently over night and by the time I woke up in the morning thier wasn't much left that was remaining. The shrimp were scowering over it. I usually throw chunks of worm in the tank for my S. Bicher but usually the shrimp go ahead and clean it up.