With the exception of Pixies or dwarf seahorses (Hippocampus zosterae), that sometimes do well raised right alongside their parents which eat the same newly hatched brine shrimp, all seahorse fry do better when raised in a separate nursery tank. There are many different designs for these nurseries, which can be asked simple or sophisticated as you please, and one of them should be just right for your needs and interests. Which design of nursery tank that may be depends largely on the type of seahorses you are raising.
If you look up my reply to a recent message titled "Re: pregnant seahorse," you will find a detailed discussion of many different kinds of nursery tanks, as well as an explanation of which type of seahorse fry are best suited for each of the designs. You can find it at the following URL and it should answer most of your questions about raising seahorses:
Best of luck with all your rearing projects, sir!