So, My betta has finally recovered from his bout with fin rot and it has made me want to upgrade his tank to a 15.125 cube rimless tank. Filled to the brim it would be almost 15 gallons, so I'm guessing at average real fill depth it'll be 12.5 to 13 gallons. What sort of accessories do I need...

I am brand new to the whole betta fish thing. How small of a tank can I get away with getting without compromising the quality of life of a single betta? Also depending on the size, what size is the biggest aquarium I can get that will not need to be filtered? I am a student and working on a...