Ah, I thought you might be in Asia, judging by when you post. That's great. Having a pond and not having to worry about heating it is a great advantage. Also, everything seems a lot more reasonably priced in Asia. You might as well get Dorado, if it's your dream fish.
Apologies for being sceptical. It's just that you sound kind of young (no offence) and over here an aquarium that size costs 5 figures and then you still have to add filtration and lighting. Now that you've clarified that your mom is putting in a pond, things add up. Good luck.