Well I want to share my experience with seahorses in case it is a help to others even though it is depressing to talk about.
I set up a 30 gallon cube tank as a species tank for seahorses last March. Before setting up the tank I did my usual hundreds of hours of research on the web including
www.seahorse.org and I planned the tank out carefully. The tank was a 30 gallon cube macroalgae tank with live rock, a few species of macroalgae, 96 watts pc lighting, tunze nano skimmer/filter combination, UV sterilizer, heater, chiller, and live rock. Basically I set up the tank right without cutting corners.
Because of delays with a vendor not sending me my seahorses for several months the tank went 6 months with no livestock in it, just macroalgae. I was happy enough with this because a more mature tank meant better conditions for the horses.
Around the end of September I ended up getting four horses (? Reidi, ID was uncertain) from a well-known vendor whom I have trusted in the past. I bought them without seeing them and they were shipped up to me. They were said to be captive bred and eating mysis well. Later I found out from the seahorse boards that they were almost certainly wild caught and net pen raised although the vendor may not have been aware of this.
In any event four seahorses arrived three months ago. Water conditions have always been perfect. The horses appeared healthy and active on arrival. However since day one they have not fed on any mysis and only would eat the small pods in my tank.
After about 6 weeks the first seahorse died, then over the next six weeks two more of the horses died, now there is only one left and I am sure it will be dead within the next month. I think the cause of death is starvation.
This has bothered me a lot because I knew seahorses would be difficult, I researched them extensively and put a lot of effort into setting up their tank.
From what I have gathered there was once a decent captive-bred seahorse industry which has been basically eliminated by competition from low-cost net-pen breeding operations. These lower-priced wild caught seahorses are from what I have read destined to die within weeks to months of purchase.
No one is proud of their failures in this hobby but I thought I should post this so others can avoid my mistake.