I know you can ship live goods through FedEx but they will charge you more.
You could always wrap up the fish, put a "FRAGILE" sticker on it and tell them it's a procelain lamp in there though...
Whatever you do, NEVER, EVER use DHL. They are the worst company ever and they don't care a single bit about respecting deadlines and they certainly don't care about complaints.
Express Post shipped on a Monday would get to destination by wednesday or thursday if shipped to or near a city. Just lie about the contents and pay for next day or so