Depending on what kind of animals you intend to have. Some people get fish and at one point i had a turtle. The aquariums are different sizes but you know just like i do animals grow. So always plan for a larger scale aquarium. that way you won't hve to buy a new one every time the animal grows. Also you will have to clean it and place your fish in a temporary one until it is finished being cleaned. then transport them back to their original fish tank aqurium after.