who said you can't??
You can import anything if you do the research and put in a submission and pay the costs
Adding fish to the import list has only been done by a very few importers.
Fish societies & hobbyist should be the ones to get involved , however they don't want to do anything.
Goldfish Have many Hazards, so hence it can't be imported.
Goldfish will be ale to be imported soon, however there are major conditions to be met by importers which will make it pointless to import.
They need to be feed brine shrimp.
The seahorse are captive breed so they eat frozen foods
I also have 3 of the Doryhamphus dactyliophorus, going to add them with the seahorses when the tank is ready.