I think what everyone is trying to say here is that this is a very complicated hobby. It requires not only a substantial financial backing to do it RIGHT, but also the patience and maturity to understand the science behind it and to devote the care required to keep it alive. I chose to use the word alive because that is what you are doing - you are taking the responsibility to provide an ecosystem that is necessary to keep these living organisms healthy, and to whatever extent they can be, happy.
At 12 years old your living situation is the responsibility of your parents. For this hobby you should be stable (as to not relocate a living aquarium) - what if your parents want to move - you have no sayso. Also, believe it or not, your interest are going to shift wildly in the next 9 years. Sharks will not be a priority in a couple of years...but that talk is for your parents. What about college? Are you going to lug a monster shark tank to some dorm room? I don't think so.
Look, we've all been there with you. And I know that at your age it might be easier to teach you latin than it is patience, but think of it this way: You'll eventually want to drive, right? Would you just jump in a car tomarrow and take off? Probably not. People are just giving you some sharp advice because they know you may waste a lot of money and the life of a very cool animal if you jump right into this hobby.
Take a step back and re-evaluate your situation. Start with a small tank and progress over the years. If at say around 25 or so you want a shark tank, go for it!
