How do seahorse eat?
 

Seahorses have no stomach or teeth. Instead, they suck their prey in through a tubular snout (a fused jaw) and pass it through an inefficient digestive system. Seahorses are voracious predators, relying entirely on live, moving food. They are opportunistic predators, waiting until prey come close enough and then sucking them quickly out of the water with their long snouts. Each eye moves independently, allowing the seahorse to maximize its search area. They will ingest anything small enough to fit into the mouth (mostly small crustaceans such as amphipods, but also fish fry and other invertebrates)

Seahorses eat non moving frozen food as well. They also often eat each others poop.

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captive raised are trained to eat frozen mysis shrimp

Seahorses have long thin snouts enabling them to probe into nooks and crannies for food. When they find food they suck it up through their snouts like a vacuum cleaner. Their snouts can expand if their prey Is larger than the snout. They are not able to chew and have to disintegrate the food as they eat it.