This is an old Ektachrome picture taken in 1967. I had three fifteen gallon tanks and I laid a single T-12 fluorescent tube across them, giving each tank exposure to about 12 inches of the tube. Not very much light. Still, I got good growth. C. beckettii is the leftmost one. C. cordata is next, and you can just see a few leaves of the C. crispatula.