Was this seahorse previously eating frozen food? Does the seahorse try to ingest food and appears to be unable to suck it into it's snout? Does it swim with a slightly open mouth? How long have you had the seahorse and where did you purchase it from? I have many more questions, however this is a good start. If the seahorse was previously taking frozen and suddenly stopped eating it is a completely different treatment protocol than a horse that was wild caught and has never been trained to eat frozen. Live brine shrimp have a very poor nutritional profile and need to be enriched prior to feeding them to a seahorse. Your best live foods are mysis shrimp, saltwater ghost shrimp or amphipods which can be purchased online. Another factor to consider is if the seahorse was wild caught it may not recognize brine shrimp as prey.

I would suggest you move this thread to emergency and I will try to assist you. Red Crest Pet Shop in Boerne also carries live brine shrimp.