Very cool. I've successfully raised seahorses myself, but it is not easy, particularly after the first week or so. I strongly suggest that once they can take anything larger than newly hatched brineshrimp you start feeding them brine shrimp that are several days old and have been fed LIVE micro algae, preferably more than one strain. To do this correctly you really need to have your own cultures of micro algae, ideally keeping them extremely clean (at least the stock cultures). It would be good to get a seasoned sponge filter into that tank soon as well, though not sure you have one available if you did not plan ahead for it. You could also (alternatively) use a rock or two of live rock, but you would need to keep this rock away from the seahorses, perhaps on the other side of a screen of some type. Otherwise 'things' will crawl out of the rock, eat the waste food and take out quite a few seahorses in the process. I found as you go forward this is the one time that a UV filter might be of value. IME seahorses have a very weak immune system, particularly if not fed a lot of varied and nutritious foods.