Aqua advisor may say the stocking level will be okay but the tank will be pretty packed I think and may appear very frantic and chaotic. Just a recommendation. That is a lot of fish in a 20 gallon.
Ok. I thought aqadvisor was a pretty accurate calculator, I've seen a lot of experienced forum members recommend it to newbies as a stocking guideline.
On another note, I've always referred to my tank as a 20 long but it's 16" tall, . I know that doesn't make much of a difference.