If the are the large type of horses, you can not raise them with the adults. They need a sterle 10 gal tank with a sponge filter and depending on the type, either rotifers or bbs to eat. if they are southern Erectus they need tiny little hitches as this type hitch at birth. all others do not hitch so you need an air line at the surface of the water so they do not snick air.
A light should be kept at the side of the tank to keep the food below the surface thus keeping the babies low in the water. Thier tank must be kept very clean so you will need to syphone left over food out and add new water several times a day.
This is not all there is to keeping babies but its a start.
Google seahorse fry and read eveything you can
TeresaQ