The most important is the minimum order amount in $, the minimum number of fish generally depends on the price of the fish. Yes cheap $.25 cent fish like neons have to be bought in larger quantities but in general they're fine shipping half a dozen of $1 fish certainly for regular customers, as long as the total amount is met.My assumption is that most all wholesalers will sell a minimum number of fish to make it commercially feasible, in the case of Saltwater fish, that might likely be a single fish... for most Freshwater fish, it's maybe closer to 50 pr more.