There are two options, declare them or don't
If you can get them ordered in from said place in hawaii from a store that might be an option? I've had friends who've ordered there and are happy and unhappy. But that is simply due to shipping. One pair made it the other did not, which i will reiterate was not the shippers fault...not at all. Just simply bad luck. Personally I have brought livestock over the border without being caught. I also purchased a dog from idaho..a Kelpie and did not declare him, din't look into it either. You can always say they were a gift

But i am not sure of the import rules on horses, which is why I used a canadian supplier, again who no longer exists. Maybe you will luck out and someone will want to sell theirs
If i remember right seahorses are on cites since around 2004-05 ?
so on second thought, i would not cross the border with them
There was a guy...on aquariumpros....Aaron ? i think who had CB Horses....but i never really looked into it.