Many have acrop tank without any direct feeding. It can grab things, such as bacteria, etc., without you doing anything special.
They do get considerable amount of nutrient from non-photosynthesis, but IMHO, there is little difference between reefer who feed the acrop, and those who don't. Obviously, some coral does not have the ability to photosynthesize, but these are not recommanded even for the seansoned reefers.