As you know, sexing adult, fully mature seahorses in breeding condition is normally simple and straightforward — the males have a brood pouch slung under their abdomens at the base of their tails and the females do not. This difference will be most obvious when the seahorses are courting and breeding, since the stallions perform vigorous pouch displays in which they inflate their pouches with water to the bursting point, making them unmistakable.
However, in actual practice, things are often more confusing, especially when attempting to sex immature (subadult) seahorses or mature seahorses that are not actively breeding. It is very difficult to accurately determine the gender of juvenile seahorses, and that may be where your difficulty lies.
If you will e-mail me at the following address, I have a well-illustrated article on sexing seahorses that I would be happy to send to you, Rani:
In fact, if you include photos of your new Tigertails (Hippocampus comes) with your e-mail, I will be happy to try to sex them for you.
Pete Giwojna, Ocean Rider Tech Support