It doesn't matter if you don't want multiple tanks now. It will sneak up on you later. You will see one at a garage sale and buy it "as a spare".
If you still have the 20 it would be much easier but you can scoop out all the gravel with fish in the tank. It is a little bit of
Howdy Bob! Welcome to AC
mini taquitos and frijoles a la charra for lunch...stuffed...need a safety nap