I keep my yumas about 3 inches below the water. I have T5 lighting about 10 inches above the water. So my lights are roughly a foot over the yumas.
I have a moderate flow that goes across the top of them. They reproduce like crazy. I feed the tank cyclopeeze and rotifers from time to time. Maybe every 2 or 3 days.
In my 65 I have MH lighting, and I keep the yumas down near the sandbed with light flow. I have not noticed any reproduction from the ones in my 65.