Hi Bonnie; I will put my two cents in since I have been raising seahorses for some time.
1st the comment about clowns I disagree with. I have a mated pair of clowns that have been with my seahorses for over a year. They stay in one part of the tank near the leather coral they are hosting and NEVER bother the seahorses much less care about them being there. I have 2 breeding pairs. My tank also sports a file fish, a mandarine dragon, and a blenny. They all live together very happily with no problems. I also want to point out that I have several people that have enjoyed my seahorse babies in tanks with clown fish of their own.
As for the comment about food. The way that you avoid feeding issues is to set up feeding stations in the tank. This is important for two reasons. It allows the seahorse to graze and it helps with the nitrate issue that you will eventually have. Yes nitrates are an issue in seahorse tanks. My seahorses feed out of a small glass dish at the bottom of the tank as well as a sun coral(helps feed the sun coral as well). There are some that use cup corals as feeding stations as well. The other good thing about feeding stations is that the ponies learn to eat in a specific area which makes it easier for them to get the food they need. My seahorses tend to ignore the mysis shrimp in favor of their own feed. While they may nip at one or two they have very little interest in the mysis.
As for losing your ponies, I agree it was just to early for them to be in that tank. Seahorse are easily poisoned by ammonia or nitrites, also how did your acclimation go with your ponies. It is very very important that they are acclimated. Here is why. More than likely there were nitrates in the tank that they came from, most fish stores are not nearly as clean as they lead people to be. Taking your ponies from a nitrate level to 0 nitrates can put your ponies in shock and they can unfortunately die from that. Wherever you get your ponies from it is very important to properly acclimate them.
I would recommend staying away from the local fish store and see if he will refund your money. One place I highly recommend for seahorses is Ocean Rider Seahorses. They are very healthy and very beautiful specimens. Another great thing is that before they sell you a seahorse they send you a seahorse training program that will teach you everything you need to know and then some about your ponies. It is an invaluable program. And as an added bonus, any ponies your purchase from them will help to conserve sea horses in the wild, so it is a win win situation!.
I wish you luck with your ponies and want to recommend that you make sure your tank is fully cycled before bringing home any more ponies If you have any other questions please let me know and I will be happy to help.