Well, firstly the 14 GBioCube is not big enough for Erectus, or really any seahorses besides the pygmys.
I've seen people put clowns with seahorses on a few occasions, but I'd say that it probably isn't the wisest decision. Clowns grab food quickly and can get aggressive, two things that aren't good for the horses.
I did raise three young H. kuda horses in a 14G BioCube, but only for 3-4 weeks to make sure they were eating, and then they were moved to a proper tank.