For the redtail catfish, arowana, and other monster fish, if price for a monster tank is an issue, you can buy one of those large stock tanks for a fraction of the price and use that temporarily. I’ve seen 300 gallon stock tanks for around $100 dollars in my area and on Craigslist. I also would not recommend getting the 75 gallon. Arowana grow very quick and will outgrow the tank in a few months (as other members have noted). If I were you I’d save money on a tank at least 200-300 if you want to keep the arowana and redtail catfish longterm. Even that is not optimal as your maintenance would have to be much more frequent and possibly aggression between fish due to territory. Again good luck! I remember when I was your age and wanted arowanas, p bass, and other monster fish. Although you seem confident that you will have the opportunity to upgrade accordingly, as a kid I had trouble getting my parents to agree on such large aquariums, especially the hundreds if not thousands of dollars. Hopefully it all works out!
Also, a 29 gallon is sufficient for those angelfish and community fish. I have kept 6-10 juvenile angelfish in a 29 gallon with no problem. However, they do get pretty large as my adult male is around 5-6 inch in height and especially if you have multiple (I think you have 1?) they will pair off and be aggressive towards each other. I also agree with Nikki about the python, literal life saver and saves a lot of time. Since I connect my python into the basement I don’t waste additional water as the pressure automatically starts the siphon. Also only around $30 so I recommend investing in that then trying to get the 75 gallon.
