Aquascaper
Fish Aficionado
Short answer......yesDavid said:One question. If tiger barbs are kept in a group of nine will they still molest the discus?

Discus are slow, peaceful fish and Tiger barbs are fast little fin nippers. Even if the Tiger barbs don't physically molest the Discus they will have a psychological impact by stressing the Discus with all their movement. Discus use small schooling fish, such as tetras, as look-outs in their natural habitat. When the small fish get spooked the Discus get spooked, and vice versa, when the small fish are settled the Discus are settled. Tiger barbs are on the move zipping around the tank 90% of the time and the Discus will see this as a warning sign and will therefore always be on edge.
HTH