CityVille Aquarium Upgrades: Everything you need to know
If you've already met those two requirements, you can head straight into the upgrade process, which is an item collection one, rather than a staff upgrade. You'll be tasked with collecting 30 items: 15 each of Seahorses and Starfish. Finishing this first upgrade not only changes the appearance of your Aquarium to something more grander, but you'll also be able to support 520 citizens, up from the base stat of 280 citizens.
If you're ready to go even further, you can upgrade to Level 3 once you've reached the 1500 citizen mark. At this point, you'll need to collect 20 each of the previous Seahorses and Starfish, which gives your Aquarium another visual upgrade, and moves the population stat to a whopping 1100 citizens. Personally, the Aquarium is probably my favorite community building in the game, so these upgrades seem incredibly worth it, but remember that they are voluntary. Feel free to upgrade (or not) whenever you'd like - they'll be here waiting when you're ready.
Will you immediately start the Aquarium upgrades in CityVille, or do you need to add some more citizens to your town before starting? Sound off in the comments.