I would go with Red Cherry shrimps, The Cyrstal red shrimps are a bit harder to keep and breed and they are more sensitive to the water qty then the Red Cherries. Try craigslist. I have seen people on craigslist have the red cherry shrimps for $1 each. I would cover the filter intake with a netting. I got some fine netting at the fabric store and used a plastic tie wrap over mine. You have to clean it out every so often so that the water flow is not low when it gets dirty and clogged. I keep endlers in with my shrimps and 1 bushy nosed pleco as they stay on the small size. I also have Assassin snails in with my red cherries and crystal red shrimps. Bigger fish will eat the babies that are born as they are really tiny in size.Make sure that you have a well planted tank to keep the shrimps. They like Java Moss
to hang out in on the surface. I have Java Moss
tied with fishing line on driftwood with java ferns that look nice.
Good scavenger is assassin snails, mystery snail, horned nerite snail, bushy nosed pleco. The white and Black shrimps are Crystal Black Shrimps the wild color of the ones created that are red and white Cyrstal Red Shrimps. get some Indian almond leaves, oak leaves as the shrimps like those and breed like crazy with some in the tank. You can get them on Aquabid, or E-bay.
Good luck with your shrimps. checkout www.planetinverts.com
for shrimp information a good website.
Here are some pictures, I know their is a gouarmi in with the crystal shrimps but these are fire honey dwarf gouarmi's and they are the same size as the shrimps and do not bother mine. If they get bigger as they grow i can move them to a 30 gal. or 20 gal. tank. They are in a 6 gal. tank in my kitchen