I'm with the others, this tank is too small for the fish selected.
Barbs are by nature feisty, and thus must be in larger groups which means more tank space. Especially the Tiger Barb which is a notorious fin nipper. We have fish profiles, second tab from the left in the blue bar across the top of the page; if the fish name shades in a post you can click it for the profile [see names below for example]. Please check the data there, it will explain this.
Red Tailed Shark
Last, welcome to Tropical Fish Keeping forum.