Well how i see the whole tank size thing is this:
Your fish lives in this tank. Is NEVER going to go out of it. Its kinda like an apartment. You can live in an apartment for ever, never leaving it *granted someone brings you food*, and only cleaning it once a month when the air is so thick you can't breathe, but are you going to be happy in it?
I have a 2 gallon *i spent $16 on it, got everything i needed other than food and water conditioner* and its not even 1' by 1' * i know this b/c the table i have it on is 1' by 1'*
try craigslist for a cheap tank or have them spend some time on here. show them some posts/threads and explain to them about the need for the fish to not just live, after all a person in a coma is alive and a person can be tortured yet still alive, but he needs to flourish. good luck! i am fortunate that my parents support me in anything i decide to do that won't get me in trouble... or include higher schooling