Thanks, @OrangeAugust and @RussellTheShihTzu for the replies :)
Unfortunately, I don't have the 20g tank. I read the ad wrong; it was 20 INCHES long...which makes it a ten gallon
So now I have two ten gallons lol.
We have soft water here. Would it be acceptable to put some tetras in a 10g or is that too small? I will be putting the betta in his own tank with some more ghost shrimp since he doesn't bother with them.