It depends what species you buy. Most are not the type that will survive well in our tanks. They're also often bred in low salinity , so you'd need to acclimate them if you want them to survive.
You shouldn't need to add any, as they'll naturally increase in numbers without something eating thousands every day.
That said, coral beauties are known to eat pods, so it could be keeping numbers low?
Some rubble in the sump with good flow will be an excellent breeding ground for pods.