Look for local fish club auctions or craigslist, very easy to breed so not hard to find. You'd do better with a sand substrate, much food will fall too far down into your gravel for the shrimp to reach. Lots of java moss and lots of light to promote algae growth for the shrimp to feed on. Once your colony gets well established you can easily pull a 100 shrimp a month to sell or for feeders.