You can tell when they mate by the greenish lumb underneath one of the shrimps tail. These are the eggs. Even if the do mate, I doubt the babies will live to maturity. Most shrimp (besides cherry shrimp) lay eggs. In your case, these shrimp lay eggs. Once the eggs hatch, they become a floating plankon that eat small debris and microorganisms. During this stage, the shrimp "fry" can be sucked up the filter, starved to death, or eaten by other fish. It is very unlikely that any of them will survive the planktonic stage, especially if you have fish. If you want to breed shrimp, I would recommend getting cherry shrimp.
