Plants and animals that pose a threat to fish: viviparous plants (bubbles), invertebrates - weevils, water beetle larvae, water bugs, dragonfly larvae, vertebrates - amphibians (tadpoles, frogs); reptiles - water snakes, birds - gulls, ducks, divers, cormorants, herons, kingfishers, ospreys and other mammals are otter, water vole, muskrat, muskrat rat, seal, fox, etc.

Insects are controlled by draining and disinfecting the ponds and, in the case of birds, by shooting them. Pests and enemies of fish can be controlled by trapping, shooting, destroying eggs (birds), caviar (frogs), and other methods. Tadpoles are caught with traps in the form of a frame net covered with a mesh of 10-15 mm. The net is lowered to the feeder, where the food is prepared in advance, and the tadpoles are collected on it. When the trap is lifted, the tadpoles remain in the net. During 1-1.5 hours, 500-1500 tadpoles fall into the trap. To reduce the number of adult frogs, they are caught with nets placed in the coastal zone. As a preventive measure against leeches, water beetles and their larvae, and dragonfly larvae, it is recommended to keep ponds and reservoirs clean, to drain them regularly, to lime the bottom, to remove thickets of tough vegetation, and to carry out other fish-breeding and reclamation measures.