Well, here is what I have found.
I was running a JBJ 36w 50/50 PC light over a 30 gallon (with about 15-20 gallons of water trying to grow Chaetomorpha.
I had NO luck p the Chaetomorpha was shrinking.
Last week, I added 110w 10000K PC lights.
My Chaetomorpha has more than doubled in size in a week.