Since the discovery of the first known pygmy seahorse species, Hippocampus bargabanti, in 1968 there has been a flurry of new discoveries. The scuba diving community appears to be at the forefront of these discoveries due to the long hours photographers and guides will spend in search of interesting creatures. Since scientists are playing catch up the second species of pygmy seahorse which has been known by divers for a few years was officially described in 2001. This was named Hippocampus denise and is generally smaller, more slender and smooth in appearance than H.bargabanti. It must be kept in mind that these amazing creatures attain a maximum size of 2cm as adults and blend seamlessly into the huge seafans that the inhabit.

These are the most well known of the pygmies and both coexist with a specific host species and are thus known as symbiotic with the host, meaning they cannot live without them. Several other species of pygmy are also known that live in close association with a host species. The colour and form of the host places strong selective pressure on the small seahorse as the more alike the pygmy is to the host the less likely it is to be spotted by predators and thus more likely to pass on its genes. Over many generations the fish will become more and more alike the host eventually blending effortlessly into their surroundings. The Red Sea soft coral and Walea soft coral pygmy seahorses are two such examples. Both appear endemic or indigenous to a small area and live among a specific soft coral. The red sea pygmy has actually been described since the 19th century and lives exclusively on Dendronepthya, a common brightly coloured coral. The Walea pygmy is currently only known from a restricted area in eastern central Sulawesi and lives in a beige, tan coloured soft coral called Nepthea.