They are open water spawners, scattering eggs at random above or among plants. You can construct killie type mops and use them to catch the adhesive eggs as they sink to the bottom. A 15 gallon long tank would be a good choice for a spawning tank. Remember the parents will try to eat the eggs, so furnish the tank with either large marbles, a net or a grid system that covers the bottom so the fish can not get at the eggs that may fall to the bottom of the tank. Add the selected fish in the evening.
Barbs tend to spawn in the morning.
If you are lucky thy will. Breeding usually is intiatd by the male, who drives the female with lots of nudging and fin nipping, which often occurs before the actual spawning. Once spawning gets started the the fish will swim side by side, pushing their bodies together with the male circling the female, forcing her into the plants or spawning mop where they release eggs and sperm. This will often take place for a couple of hours before the pair lose interest in each other. At this point the fish should be removed from the breeding tank before they start searching for and eating the eggs they've just released.