sick seahorse?

[tanakiye]

I bought a seahorse a bout a week ago..shes been living in a very well established nano-reef. It's been feeding well on live brine and pods growing int he tank. It's been exploring the tank and seemed to be doing good. Today it refused the brine and has spent most of the day sitting in one spot. It doesnt really look sick, coloring is the same...occasionally it does this 'throat-flexing' thing, and it looks like its lifting its head and jerking it slightly..almost like its snapping up some food but i dont see it eating anything...The water quality in the tank is always perfect, temp stable at 79 and ph at 8. I did a partial water change two days ago..i do this every week. The other inhabitants...xenia, mushrooms, clam, feather dusters, porcelain crab and hermits..all seem to be doing great. Is this seahorse sick or do they just do this sometimes? I've heard of something called hydroids...could this be that?

thanks!