Such corals dont need lot of light. Still light schedule have to be related to light power. High power lights / shorter timing; low power lights / longer schedule. MH users keep them 4-6 hours / day.
Also, keeping lights too much ON, may encourage algaes to grow.
I am using leds with 12 hours blue/UV, but 2 hours ramp up and 2 hours ramp down (basically 8 hours at full power) and white channels at 10 hours, but again with 2 hours ramp up and 2 ramp down.
In the end, anything between 8-12 hours works. Can be a bit lower when you fight algaes, but no more than 12 hours as corals need to "rest"