Ok well first off it’s nice to see another 17 year old that’s into fish.
Second, I truly don’t think that a 3 meter width is needed for any of those fish.
Third, you can actually get giant “tanks” made and sometimes even shipped to you depending on where you live. Talk to
thebiggerthebetter
about his 4,500 gallon tanks.
Fourth, I would also talk to
A
arapaimag
since he built a 15,000 gallon and a 50,000 gallon tank himself.
Fifth, I would go to the diy section of this site and take a few days or even weeks to go and look through the threads. There have been a respectable number of threads showing people building huge tanks.
Sixth, I’m overjoyed that someone my age is into it but just remember to take your time in this hobby. You have your entire life ahead of you to keep fish.