I think you mean 3 leds to a metal core PCB.
It is not only about how many LEDs but how many watt LEDs you are using.
Unless your tank is less than 12 inch deep.Only 3 watt LED can penetrate
the water deep of more than 12 inch with the help of optics.
If I am not wrong your LED lite cannot even meet the spec of a 70 watt MH
Read more before you invest
Cheers