No problem at all. The barracuda would eat them without any trouble.
There are actually only a few fish that are compatible with seahorses, barracuda aren't one of them.
All seahorses are of the genus Hippocampus, and black is not a species and means nothing. Seahorses change colors. Black is actually a sign of a stressed seahorse.
If you want to get ponies, please get them from a reputable source. I can put in in touch with a couple breeders, it will save you lots of heartache and money in the long run.