What is the reason for the nail tail of bullfrog tadpoles?

Insufficient nutrition. The phenomenon of iron nail tail and triangular head appears in tadpoles of bullfrog, which is caused by insufficient nutrition. The snail pond has a small water body and weak buffering capacity. In addition, due to the Qingming solar term, the temperature difference between morning and evening is too large, and the fat water can't get up. When the water gets together, it will be green and thick, which is not conducive to the early growth of snails, and it is easy to cause the python to be completely annihilated.