First off could you read the links at the bottom of
'Thoughts on Seahorse Keeping.
Those links will give you some basic understanding of seahorse needs.
While some people seem to luck in and have no problems with the seahorses they buy under many varying conditions, most people don't have the same luck and are fraught with problems that lead to deaths.
There sometimes can be problems sharing water as many seahorses can't seem to deal with pathogens they get exposed to from other fish or seahorses from different breeding sources.
This can be extremely important if you want to try mixing pipe fish with seahorses as almost all pipefish are wild caught and present pathogens that most seahorses haven't been exposed to and may succumb to.
I've heard that sometimes ORA has aquacultured pipefish for sale, but I haven't read of anyone trying to mix them with seahorses so I can't advise on their use.
Unfortunately in this hobby, some people posting success using non recommended situations lead many others to do the same but with disastrous results more common than successes.
I'd suggest trying first to succeed using the most recommended methods before trying others.
