It sounds like your Hippocampus barbouri are eager to breed and mate, but that they are having difficulty executing the egg exchange, and spilling the eggs rather than successfully transferring them to the pouch of the male.
There are two main reasons why this can happen. If the aquarium is not tall enough, the ponies may not have sufficient vertical swimming space to correctly align themselves for the egg transfer, resulting in the eggs being dropped on the bottom of the tank. Or, it’s possible that there could be too much turbulence or that the water currents are too strong in midwater, making it difficult for the partners to complete the egg exchange.
If there is not enough vertical swimming space, there may simply not be enough maneuvering room for the pair to successfully execute the copulatory rise and transfer of the eggs when mating. Allow me to elaborate. The following information will explain more about the copulatory rise and how mating occurs to seahorses, and why it’s important for them to have plenty of room in order to perform the necessary maneuvers in order to accomplish the transfer of eggs:
This is the final phase of courtship. It is the climax of the entire affair during which the partners meet in midwater for the transfer of the eggs (Vincent, 1990). The female initiates the rise by pushing up from the bottom in mid-Point and the male immediately follows her lead. They ascend through the water column facing each other, with their heads raised high and their abdomens thrust forward (Vincent, 1990). At this point, the female’s genital papilla or oviduct will be everted and protrude slightly from her vent, and the male’s brood pouch is usually fully inflated (Vincent, 1990). As they ascend, the female often continues to Point and the male may continue to Pump (Vincent, 1990). They will meet at the apex of their rise for the nuptial embrace.
The actual transfer of eggs takes place while the couple is suspended in midwater or slowly descending toward the bottom — a maneuver that is every bit as tricky as it sounds. Coitus is marked by an extremely awkward, fleeting embrace, aptly described as little more than a brief belly-to-belly bumping (Vincent, 1990). (Brief and fleeting as in if one dares to blink, take a bathroom break, or run for your camera, you may miss what you have waited all this time to witness!) As you can imagine, many difficult and delicate maneuvers are required to bring the pair into proper position for this most improbable merging. The female will attempt to insert her oviduct into the gaping aperture of the male’s inflated brood pouch. An inexperienced pair will often end up misaligned, perhaps at right angles to one another or with one of the partners too high or too low to join. This is very typical of the many false starts and abortive attempts that are ordinarily involved. The frustrated couple will separate to rest on the bottom prior to successive attempts. They may require many such rises before the proper positioning is achieved and the crucial connection is finally made.
The female will eventually succeed, with the full and active cooperation of her mate. He positions himself slightly below his mate, with the aperture of his pouch fully dilated and gaping open, ready to receive her eggs. The female will hover directly over the aperture until she can actually insert her oviduct into the opening at the top of his brood pouch or drop her eggs into the basket while hovering directly above the pouch. Pairs occasionally entwine tails when joined, but more often than not their tails will be stretched back behind them, out of the way.
If she makes a good connection, she will extrude her eggs in one long, sticky string, and the pair will hang together in midwater while the transfer is completed, drifting slowly downward as the eggs surge downward deep inside the pouch (Vincent, 1990). The entire clutch — up to 1600 eggs — is transferred in one brief embrace lasting a mere 5-10 seconds (Vincent, 1990). Sperm streams from the male’s urogenital pore into the pouch opening as the eggs are deposited (Vincent, 1990). The couple separates as they descend, drifting slowly toward the substrate. Exhausted by their efforts, the pair seek out comfortable hitching posts for a well-deserved rest. One almost expects to see them light up cigarettes at this point.
Strong water currents or a lack of vertical swimming space can disrupt the egg exchange, so those are the first things you should double check in your seahorse setup. If these are new pairs, it’s also possible that they simply need a little more practice before they get it right, so this may be an issue that your Hippocampus barbouri will eventually work out for themselves, as well.
Pete Giwojna, Ocean Rider Tech Support