A hindrance to wider adoption of augmentative biological control is the high cost of mass production of natural enemies, such as predatory insects. Cost reduction could occur by mass rearing of predators on alternative foods and artificial diets rather than maintaining live prey and host plants. Many of the experimental foods and diets tested thus far are suboptimal, in comparison to optimal prey, and cannot serve as a standalone food source. In this study, we tested the hypothesis that Spirulina platensis (Cyanophyceae: Phormidiaceae), a protein- and vitamin-rich cyanobacteria microalga, could serve as a supplement to suboptimal diets for the omnivorous, ladybird beetle Coleomegilla maculata (Coleoptera: Coccinellidae). We conducted feeding bioassays to determine the effects of adding S. platensis powder to suboptimal food - synthetic pollen (Feedbee®) and a prototype artificial diet (based on vertebrate protein). We also determined the nitrogen, hydrogen and carbon content in dried samples of experimental foods. We discovered that S. platensis supplementation had little or no beneficial effect on increasing the quality of the synthetic pollen or the artificial diet. The higher nitrogen content (a measure of crude protein) of S. platensis, in comparison to synthetic pollen, artificial diet or Ephestia kuehniella (Lepidoptera: Pyralidae) eggs, did not mirror its usefulness as a supplement in either suboptimal food. S. platensis had detrimental effects on the health of C. maculata when used at moderate to high concentrations in this study. From this study, we surmise that a high protein content in food (as in Spirulina) does not necessarily ensure adequate development and reproduction in C. maculata.