yeah with that size tank you're already fully stocked, if not overstocked. the silver dollars get huge, the tinfoils get huge, the dinosaur bichir gets huge, the peacock eel gets biggish. the brown knife gets big, and i dont know what a silver shark is.. but if it's a columbian shark/catfish then it gets big too.
as it is now, your barbs will probably eventually all get eaten. the peacock eel will probably get badgered and then eaten. eventually you'll be left with 2 silver dollars, a tin foil barb and a bichir. when that happens, i'd upgrade to about a 200 gallon aquarium so you can fill out the schoolsof silver dollars and tin foil barbs, and then you could probably put some large cichlids in the tank as well.. as long as they're not overly agressive, and there's lots of large hiding spots.