Joint cultivation of fish, bivalves and vegetable crops using floating beds

The results of joint cultivation of crucian carp, painter’s mussel with tomatoes and bell peppers on a floating bed placed directly in a fish tank in an artificial ecosystem during operation of installations with closed water use in order to identify the features of their joint cultivation are presented. At the first stage, one 20-liter container equipped with water circulation contained a monoculture of painter’s mussel (9 specimens), the second container contained 9 painter’s mussel and 4 crucian carp fingerlings, and the third contained only 4 crucian carp fingerlings. Dry granular compound feed was added to all three containers at the rate of 1.0–1.2% of the weight of living organisms per day. When fish and shellfish were kept together, compound feed was added in terms of ichthyomass. At the second stage, two 200-liter aquariums with water circulation were used, which contained 7 crucians each and placed floating beds in which 5 tomato bushes and 3 bell pepper bushes were planted. An additional 20 painter’s mussel were added to the experimental aquarium. It was noted that the body weight of fish kept together with painter’s mussel increased by 69.7% of the initial weight, while the weight of fish in the group without shellfish increased by only 41.1%. The survival rate of painter’s mussel in the presence of crucian carp reached 100%, compared to 56% in the monoculture of shellfish, which can be explained by the appearance of fish excrement and associated detritus, a food source for shellfish. At the same time, feed costs for fish weight gain decreased by 20%. In addition, additional painter’s mussel biomass production in the amount of 752 g was obtained in the polyculture, increasing the total bio-production by 3.5 times. Despite the multiple increase in the total biomass of aquatic organisms, plants on floating beds ensured the maintenance of acceptable hydrochemical parameters. The ratio of hydrobiont biomass to plant biomass in the multiculture variant was 5:1.