Fish compatibility question?

I have 2 Blackskirt hi fined tetras, 1 red fined tetra, a inca snail, a small bottom feeder that was rescued, 4 platies and 2 "sharks/catfish" they all get along great, but I was wondering if this is too many fish for my 20 gallon aquarium? I wanted to add some new things to my aquarium and was thinking of one or two more fish and some more plants and decor. Any suggestions? I was thinking of some Giant Danios or Dwarf Gourami. Keep in mind, I've had this set up for over a year and a half, the fish are happy, healthy and get along great. Looking for kind suggestions, rude comments will be ignored. Thanks to all that participate!