Dear ageber:
I’m sorry to hear about your missing seahorse. That’s quite a puzzle and I’d be happy to share my thoughts on the matter with you for whatever it’s worth.
I don’t think you’re serpent starfish could have consumed the juvenile Sunburst. As you know, the starfish has no teeth and cannot chew; it must swallow its meals intact and in one piece, so that anything that is too large for it to stuff into its oral cavity is quite safe. If it had eaten anything as large as your juvenile seahorses, it would be immediately apparent. The body disc of the serpent starfish would be enormously swollen and distended and you could probably clearly make out the outline of the seahorse inside of it. I know that when I feed my serpent starfish pieces of cubed cocktail shrimp, you can clearly see a square lump in the body disc of the seahorse for each piece of the cocktail shrimp it has ingested. So check out your serpent starfish for any suspicious lumps and bulges in its central disc — if it had eaten a meal the size of your seahorse, it would be grotesquely engorged; if it is not, then you can be very certain that the serpent starfish played no role in the disappearance of the seahorse. It is a cold-blooded creature and its digestion is therefore relatively slow — if it had eaten a large meal last night, it would still be extremely evident today simply by examining its body disc.
Due to the bony plates that comprise it’s exoskeleton, a seahorse that has been killed or died doesn’t decompose and disintegrate overnight. Unless you’re serpent starfish is enormously fat and lumpy this morning or one of your sand sifting starfish has somehow managed to bury the carcass, the seahorse must still be in the aquarium somewhere in some inaccessible nook. Nor could Nassarius snails and bristleworms or other scavengers dispose of a deceased seahorse in a single night.
One possibility that occurs to me is that a mantis shrimp may have hitchhiked into your aquarium on the live rock. A large stomotopod is quite capable of killing a juvenile seahorse and dragging it into its hiding place within the rocks. (Indeed, I have lost a seahorse before in this identical fashion myself.) If that’s the case, you will need to trap the culprit and remove the mantis to prevent any further depredations.
Hopefully, your juvenile Sunburst has secluded himself out of sight and will emerge none the worse for wear at your next feeding. That’s quite possible in a 90-gallon aquarium with lots of live rock. But it’s also entirely possible that the seahorse has expired for reasons unknown and that you will never find it. That has certainly been known to happen in a large aquarium aquascaped with lots of live rock and live corals to create an intricate environment with the varied microhabitats seahorses need to thrive.
Keep an eye on your water quality for the next few days. If the seahorse is deceased and decomposing somewhere unseen in the aquarium, there may be an ammonia spike as it decays. In a large aquarium like yours, with sufficient water volume to provide a generous margin for error, and plenty of live rock for efficient biofiltration, there may be no ammonia or nitrite spikes following the undetected loss of a seahorse, but it’s always best to play it safe and monitor your water quality for the next several days.
Best wishes with all your fishes, ageber.
Respectfully,
Pete Giwojna
Ocean Rider, Inc. is an Organic Hawaiian-Based Seahorse Aqua-Farm & Aquarium that Follows Strict Good Farming Practices in Raising Seahorses and Other Aquatic Life.
