My bad, I didn't see the 20 gallon long in the top. That was what I needed to know.
You can somewhat reasonably stock a 20 long as if it were a 29 standard, but that needs to be modified a little bit...the pollution levels of the Cichlids would be the same, they'd just get the 29g surface area for aeration.
I would think that you could stock it like a 25 gallon for Cichlids, but I would have to have someone confirm it, as I'm now delving deep into the realm of theory.
Someone else will hopefully be able to run with that.
Matthew