You can run two single units from a single larger pump if needed. Use a 'Y' splitter from the pump to feed the two outlets.
Having the two overflows provides a higher degree of flexibility in water flow as each outlet can be angled in a different direction. It also makes for a very low profile an stunning display
A Minimum flow of 1056GPH or 4000L per hour is required.
DC pumps like the Jebao DC 9000 are recommended as they allow a high level of adjustment to tune the flow of water.