Tilapia are mouth breeding herbaviores and detritivoires.
Here is an interesting article
http://www.aquanet.com/features/tilapia/perfectfish.htm They are able to digest cellulose, like a cow, and there fore can eat and digest detritus (aka loon shit). Most fish do not use this as a food source. Detritus is a very poor food source for pretty much everything. So when they have the oportunity to eat algae they probably do even better. Algae has a low c:n ratio and is good forage.
