I was told when buying a selected gender desired, one has to buy both sexes and then the fish can be tested and selected for the desired sex. In other other words, selling single sexed fish may or will throw off a sellers 50/50 mix and the next buyer of fish may suspect he will get or has gotten a non-desired mix. So you will most likely buy both sexes and then have them tested for gender, driving up the cost of your selection.
