I have a 40 polyp sun that is bigger than a softball. I have found that the light is not the issue, the current is key. I moved mine from a cave to a plastic hanger I made. It is 6 inches under the surface and in the light. I hold a bit of frozen plankton in the current for a minute, and in 10 minutes it is wide open. Also, phytoplankton???? Mine consumes frozen BRINE and MYSID. About half a cube per feeding. To avoid fowling the tank, I feed the sun and the fish get the leftovers.