Not crampin on your style but.... You will be lucky to keep the Neons in conditions like this. They are a pretty sensitive fish. I have not been successful with keeping them and my water parameters are very good and its a planted tank. As for your dream fish. It can grow to 16+ inches. You will need a much bigger thank, then if the neons are still alive it will eat them as it grows. I am not a stocking pro as I am working out my own issues but just from my experience.
Thats why i don't have one lol i want to have a big enough tank before i even get one, and my neons are healthy as can be lol mines non-planted as of now, well except for 2 moss balls but those don't count haha i also have a power head and a air stone they seem to really like the bubbles
29 Gallon: 7 Neon Tetras, 5 Glowlight Tetras, 2 Pleco, and 2 German Blue Rams!!