I have 6 living in my refugium they are Palaemonetes vulgaris and I got 25 of them from
http://www.aquaculturestore.com/. They are fun to watch as they are very lively and a couple are gravid. I bought live mysids at the same time and I think they ate them all, so I would not really recommend them in a fuge. I am going to move them to a little 3 gallon tank and re-populate the msyids. They have been in my tank for months at a specific gravity of 1.026