Yes, sir, the Hippocampus fisheri are quite compatible with the Ocean Rider banded pipefish and would do well in an aquarium designed for the good-sized banded pipes.
Although they are relatively small, the Hippocampus fisheri are deep water, open-ocean seahorses that remain pelagic (i.e., free swimming) all of their lives, and they are therefore active swimmers that require more swimming room than other seahorse species of similar size.
I recommend a tall tank of at least 30 gallons for both the Hippocampus fisheri and the banded pipefish for best results.
I will send you a document that discusses the aquarium requirements for Hippocampus fisheri in greater detail via e-mail, Don, so that you can download the document, save it on your computer, and then read through the information at your convenience.
Best wishes with all your fishes, sir!
Pete Giwojna, Ocean Rider Tech Support