Most fish, including clowns, will eat the food before the timid seahorse can get any.
Often, even the movement of a fast moving fish can stress them so they don't eat.
I lost a cleaner shrimp to my Reidi's when they worked together and pulled it apart to eat smaller pieces.
For best chances of success with seahorses, stick to a dedicated tank where you can keep the temperature 74°F or a bit lower as seahorses are VERY susceptible to bacterial infestations.
Bacterial infestations increase exponentially. especially above the 74°.