I'm sure the info provided by the above poster is totally valid
3nodding However, I thought I'd just add some basic info on taking care of your Aquarium --
Generally, your aquarium will look like a dirty mess if you've neglected it for a while. If you visit it daily, or just a few days per week, feed your fish, change the music, & press the "save" button, you should be fine.
Be sure to visit your Aquarium daily for daily rewards from the "overseer" [that would be the shining clam thing].
For further info, you might want to check out these guides:
Wet N' Wild - A Guide to AquariumFish Lab - A fish happiness guide