The purpose of this study was to test in the bee's feed the biomass of aquatic microalgae Scenedesmus quadricauda, hereinafter referred to as bioactive supplement "Scenecuadri" and elaboration on its basis of a process of feeding of bee families during the end of winter and start of spring (february-march), poor harvesting period in nature. The researchers was conducted on the Apis mellifera Carpatica bee families at the experimental apiary of the Institute of Zoology of the Academy of Sciences. For testing of biomass in bee's feed at the end of February, they were formed three batches of bees families, to which once for each frame with bees were administered 200 g of nutritional paste, prepared by mixing the powdered sugar with honey in proportion 7:3. The batch I - control, bees have received only nutritional paste, prepared by mixing the powdered sugar with honey. The batch II - the bees have received paste enriched with nutritional supplement “Apispir + Cr" in quantity of 200 mg of active substance per 1 kg of paste. The batch III - bees have received nutritional paste enriched with bioactive supplement "Scenecuadri" in a quantity equivalent to 200 mg of dry substance per 1 kg of paste. Research results have shown that feeding of bee families with nutritional supplement enriched with biomass of aquatic microalgae S. quadricauda help to increase, compared to the control batch, queen prolificacy up to 125 eggs or 7.8%, the amount of capped brood with 14.7 hundreds cell or 7.7%, family power by 0.30 kg or 9.3%, the amount of bee bread accumulated in nest with 14.0 hundreds cells or 15.5%, the amount of wax increased by 0.04 kg or 13.3%, resistance to disease by 1.6 or 1.8%, brood viability with 11 points or 1.2% and the amount of honey in the harvesting 3.01 kg, or 27.6%. The result is due to increasing nutrient assimilation and accessibility of biomass, given the fact that the microalgae Scenedsmus quadricauda is covered with a thin protective membrane and the biomass is rich in biologically active substances, in particular proteins, carbohydrates, lipids, essential amino acids, micro - and macro elements, antioxidants (beta carotene), which have a catalytic role in the metabolism of substances nitrogenous to worker bees, participates in the synthesis of enzymes, improves the qualitative composition of royal jelly and stimulates its secretion by wet nurses-bees, so indirectly influence (by feeding with royal jelly of the queen) on the reproductive system of the queen, intensifiing the ovogenesis and eggs laying. All of this largely determines the queen prolificacy, development of the larvae and brood from the nest, contributing to the increased family strength and their productive potential as a whole.