Growth. Most tilapia farmers consider fast growth from seed to harvest size to be the most important performance trait, along with high survival rate. The efficiency with which a fish converts feed to body mass is also an important consideration. However, for the majority of tilapia farming systems prevalent in Asia when the development of GIFT started, growing fish quickly to harvest size, even with ad libitum feeding, was the overriding concern. These farming systems comprised mainly fishponds, fertilized to produce natural plankton as feeds and also supplied with supplemental feed, and cages in which fish were usually supplied with more complete formulated feeds. In these situations, there is sometimes a tendency to overfeed fish in the belief that this will lead to increased harvests. This situation complicates estimation of feed conversion efficiency. Methods for the genetic improvement of feed conversion efficiency in farmed fish were not available when GIFT were developed and are still under development.22