Although I've never owned much of an aquarium, this video of the worlds second largest aquarium, makes me desire to acquire another...
I think the salt water tanks are most attractive with all the colorful fish.
But with fresh water, you can get those little baggers to grow full size, if you have the area to allow them, to their full potential.
Red Bellied Pacu are so friendly, you can practically hand feed them. Smile, NOT!!
I also like those baby sharks...