Also if the seahorses eat the eggs or egg leftovers, it can get caught and kill them. Always when hatching pull from the bottome your your hatchery. Shine a light at the bottom cause the brine are attracted to it. All the unhatched stuff usually will be at the top so you don't have to worry about harming your seahorses. The best way is to screw a valve at the bottom of the bottom so you can open it and pour some brine into a net and then feed.
With an empty soda bottle all you do is cut the bottom off it and flip it upside down ( so the spout is on the bottom). The figure a way to keep it held up, then toss in an air stone and some water and you have a hatchery. Change the water when you need to and dump some phyto in the bottle to feed them.