This chapter discusses the relationship of assimilation efficiency and food quality later. It also discusses the capture rate and clearance rate are considered to be synonymous; this is also so of feeding rate and ingestion rate. Feeding rate is also affected by temperature, life stage, particle size, light regime, and many other factors. Food quality and quantity, and the effect of environmental variables, influence feeding rate and thus promote efficient utilization of food resources. In examining food quality and growth, it is thus important to examine the effect of temperature, as this, assimilation, and food quality are closely interlinked. In experiments to test the effect of food quality on growth, it is important to consider the effect of temperature and, if possible, to control this variable in the experiments. Food quality is therefore important in controlling growth rate and it can override the effects of temperature, although food quality can, in turn, be affected by temperature.