The scientific lecture with the title of "Mass culture of phytoplankton useful in feeding silver carp (Hypophthalmichthys molitrix) and their injection into farm ponds to increase production per unit area" was held in the conference hall of the National Inland Water Aquaculture Institute – Gilan. The lecture was delivered by Dr. Seyed Mohammad Salavatian on July 12, 2020. The silver carp (Hypophthalmichthys molitrix) is a filter feeder. This fish feeds on planktonic organisms, especially phytoplankton. In warm-water fish ponds due to fertilization, a community of different types of phytoplankton is formed. Some types of phytoplankton are filtered by the filtration system of fish gills and enter the gastrointestinal tract, while others are not absorbable and do not enter the fish digestive tract. In addition, some of the plankton that pass through the filtration system of fish gills and enter the gastrointestinal tract may be poorly digestible and the fish may not feed on them. Therefore, part of the fertilizer used in the pond may always be used to grow and increase the population of phytoplankton that does not play a role in feeding the silver carp. This group of phytoplankton can be considered as unwanted phytoplankton. The presence of these phytoplanktons in the pond, and especially their dominance, on the one hand increases the cost of production and on the other hand reduces the growth of fish which can ultimately lead to a decrease in production. The abundance of unwanted algae has an effect on the water chemical regime and creates problems such as lack of oxygen, etc., which requires aeration systems and spending time and money to solve this problem. Therefore, if it is possible to mass - produce a variety of phytoplankton useful for farming warm - water fish and introduce them to the pond so that fish can easily filter these phytoplankton and have a high nutritional value, it can be expected that production per unit area will increase significantly and production costs will decrease.