You need mysis or other suitable sized shrimp (ghost, glass, grass, lava, skeleton etc.), period. That is what they eat. Find the food, or give the seahorse up. If you live someplace where you can order it online, then do that, otherwise, find a way to collect it or otherwise obtain it yourself. Adult brine shrimp might work, but you need to obtain them live, as adults. Baby brine, brine cysts, phytoplankton, zooplankton, pellets, etc. will not work.
Continuing to post that you aren't giving the seahorse suitable foods just riles people up and makes them think that you don't understand what they are saying. They are going to keep trying to explain to you for the sake of the fish, until they get angry and frustrated and this thread goes downhill like your other threads. It just isn't worth the energy on either end.