Opinions: Is my tank too crowded?

I currently have a 20 gal tank running with an undergravel filter and a powerhead for improved suction and circulation. The residents of my tank include 1 Rainbow Shark, 1 Opaline Gourami, 8 Harlequin Rasboras, 4 Hengel's Rasboras and 3 Otocinclus. Do you think it is too crowded? If yes what do you suggest I do? Please note that the Rainbow Shark is my baby and I could never part with him. Thanks.