+1ming said:You shouldn't have to feed an acan. They can survive and grow fully with proper lights. feeding them is only supplemental to help it grow faster, not to be used as a substitute to bad water or improper lights.
I Feed my acans twice a week, Its not necessary to spot feed them if you do it will def help with growth and health, but to answer your question as long as they are grabbing some type of food from the water column whether it be phytoplankton or any other small particle food source they'll be fine without it. The color mostly depends on the lighting and placement of the specific specimen.