LoopTech,

In my experience, regular artificial feeding reduces Tilapia effectiveness on algae control by about 50%. However, I've also seen a cumulative effect from Tilapia such that after several years of stocking, the amount of pre-season algae is less each year. Hence, I can stock at a lower rate in my artificially fed pond after several years than I otherwise could have for effective algae control.

Supporting data from SRAC: "In heavily fed ponds with little or no water exhange, natural food organisms may provide one-third or more
of total nutrients" Reversed, this means to me that a Tilapia will eat up to 66% more algae (natural foods) in the absense of artificial feeding which tends to match my experience.