I just picked up a 20 long today, and I was planning to divide it for multiple bettas. I have one grumpy old one who doesn't move much (and honestly seems overwhelmed and stressed by the space he has in his 5g) that I was planning to give 3-4 gallons... but I have no idea how I'll divide the rest! I was thinking of doing the 3-4 gallon compartment, and then 3 others equally sized in the rest of the space.
Or should I just give him his little compartment and then have the rest of the tank be open for something else (not bettas)?
Is this even a good idea? If it is, any ideas for compartment size?
As for filtration, I was planning to put either a big filter in the middle or put a smaller filter at each end. which is more advisable? I know that bigger particulate won't make it out of the compartments easily, but that's what gravel vacuums are for :p