I think it depends on how much they'll have to eat, and how many things will be eating them (and how soon). If you have a mandarin goby, you'll need a lot. If you have nothing to eat them, and some chaeto or algae on your rocks, then one jar (i.e. DT's Live Pods) would multiply in a few weeks or months. If you have macro/chaeto in a refugium, you probably already have some, you could add more to there and they will multiply.