i have a seahorse tank that has 2 false percs, 2 pj cardinals, 1 yellow wrasse, 1 algae blenny, 1 scooter blenny and 1 coral beauty.
the flow is not strong but i have lots of different filtration methods.
As long as water quality is HIGH, flow is low in the areas they hang out most, they have good hitching posts and the tank mates do not eat their food or harass them, then its good to go.
however, its always better to add the seahorse first, not last.