1. It is generally a good practice to purchase the largest aquarium that you can actually afford. A larger aquarium will be less susceptible to quick changes in the chemistry, and will offer much more stability.
2. You should keep some brushes on hand, especially if you are a reef aquarium owner. With your brushes you will be able to clean off any built up grime from inside your aquarium or on the surfaces of your hard corals.
3. Stingrays make wonderful pets for the aquarium, but make sure you can properly care for your stingray in your home aquarium.