You won't be able to breed ghost shrimp in your sump, since the various species that get lumped into the common "ghost shrimp" are freshwater shrimp. I am not certain about the optimal conditions for breeding ghost shrimp, but I did have a few ghost shrimp that were breeding, quite accidentally.
You should have a mature freshwater tank, preferably planted with real plants, and no fish or inverts other than the ghost shrimp you are breeding. Most fish will eat the ghost shrimp larvae, and other shrimp may be opportunistic predators. Cover any filter intakes with nylon stockings to prevent shrimp larvae to get sucked in. A heater may not be necessary if ambient temperature does not drop below say, 65 degrees, but I am not certain of this - I kept my setup at around 74 degrees.
Female ghost shrimp will naturally become pregnant in the presence of males, and the green/yellow eggs will hatch into larvae in about 3-4 weeks. Larvae take about a week to develop into juveniles, and while in the free-floating larvae stage, they will eat mostly infusoria (hence the need for a mature tank). I also fed some fish food intended for very small fry, but I don't recall the larvae feeding on those.
Overall it should be relatively simple to breed ghost shrimp, you may even be successful without a fully mature planted tank.