This might be an old hack for Happy Aquarium, but for some of you it may still work. Most of you will not be able to do this, but it's always worth a shot, right? It's a cheat from 9/29/09 (wow!—retro hack) for which you need Cheat Engine 5.4. Newer versions of Cheat Engine should work, too.
To do this Happy Aquarium hack, perform the following steps.
1. Open Cheat Engine.
2. Open Happy Aquarium.
3. Choose your web browser in Cheat Engine (either firefox.exe or explorer.exe).
4. Click OK.
5. Enter the number of XP you currently have.
6. Click on the First Scan button.
7. Start playing Happy Aquarium—earn some more XP.
8. Once you earn more, go back to Cheat Engine and enter the new amount.
9. Click on the Next Scan button.
10. Choose the last number in the list.
11. Click the red arrow.
12. Double-click on the Value and change it.
13. Click on Frozen.
14. Go back to Happy Aquarium and earn some more XP—again.