Instructions
Navigate to Gaiaonline.com, log in and click "Shops" on the main menu bar.
Select "Shops Directory" from the drop-down menu, then scroll down to aquarium and click "Phin Phang."
Click "Enter" to bring up the shop's inventory, then click the "Fish" tab. Scroll over each fish to view the name and price. Select the "Aquarium Dolphin" for 499 Gaia Cash.
Click "Buy" in the pop-up dialog box, and again to confirm the purchase with the shop's proprietor.
View the dolphin by clicking "Go To My Aquarium" on the left side of the screen.