What to Do When a Farm Pond Turns Over? A Detailed Guide to Emergency Treatment Techniques

Pond “turning over” in aquaculture is a fairly common phenomenon. During the farming process, sometimes the pond fish are eating well one day, except that the pond has a fishy, foul smell, and the next morning the fish are found all floating at the surface, and by noon they still have not gone down; running the aerator brings no improvement, and they may even stay up for several days and nights. At this point, you should consider that the pond has “turned over.” The following are emergency treatment techniques for pond “turning over” in aquaculture.

In recent years, because of this kind of sudden deterioration of water quality, pond-wide fish kills have occurred repeatedly, causing major economic losses. Below, we introduce the emergency treatment methods for pond “turning over” in aquaculture. So-called “turning over” refers to a severe shortage of the water body's oxygen-producing capacity and self-purification capacity, resulting in extremely low dissolved oxygen levels in the water, with harmful gases and substances accumulating in large amounts, which in turn causes the pond fish to float at the surface for a long time. Signs in aquaculture production: with normal or abruptly changing weather, the water changes from oily green to tea-brown, sometimes with a fishy, foul smell; there are not many fish in the pond, yet they float at the surface for several days without sinking.

I. The process of “turning over”

“Turning over” makes the pond water change abruptly from its original deep green, blue-green, or tea-brown to milky white or dark black, and afterward it gradually becomes clear and transparent. In this kind of water body, very few phytoplankton remain, photosynthesis is weak, and on top of the already high organic matter content, large amounts of dead phytoplankton debris are added, so the oxidative decomposition of organic matter is very intense. The concentrations of toxic products from oxygen-deficient decomposition of organic matter (such as molecular ammonia, nitrite, hydrogen sulfide, and methane) rise sharply. If blue-green algae are the cause, some special toxic substances (hydroxylamine, hydrogen sulfide, etc.) may also be produced.

II. Causes of “turning over”

First, the proportion of plankton in the fish pond is out of balance, with too much zooplankton in the water body, such as rotifers and cladocerans, which consume large amounts of phytoplankton; the reproduction rate of phytoplankton is lower than the rate at which zooplankton consume it, causing zooplankton in the fish pond to reproduce excessively while phytoplankton are consumed until none remain, so the water body's oxygen-producing capacity becomes extremely low and ammonia nitrogen and nitrite become too high, that is, “turning over.” Second, after sudden weather changes, application of drugs, and so on, large amounts of phytoplankton in the water body die, causing a sharp drop in dissolved oxygen in the water and excessive ammonia nitrogen and nitrite. The two can be distinguished by microscopic examination: in the former, large numbers of rotifers and cladocerans can be found in the water body, while in the latter there are none.

III. Warning signs of “turning over”

Before “turning over” occurs, there are mostly warning signs. The usual signs of “turning over” are: the water body is too fertile, mostly deep green, blue-green, or tea-brown; the water body turns black or red; when the aerator is running, the water body has a fishy, foul smell and gives off large amounts of foam; the pond fish feed slowly and eat less.

IV. Emergency treatment of “turning over”

The most direct and most effective way to deal with “turning over” is to change the water: add new water while drawing off bottom water. For ponds with limited water sources, chemical drugs and physical methods can be used to regulate water quality: Step one: turn on the aerator. Step two: reduce harmful substances. Step three: fertilize the water. Fertilizing the water is a main measure that must be taken after treating “turning over.” After the water quality treatment is finished, you can apply water fertilizer such as “fertilizer essence” or “fertilizer pioneer.” Because after “turning over” the total nitrogen content in the water body is generally high, adjusting the nitrogen-to-phosphorus ratio of the water body is beneficial to the growth of phytoplankton and also lowers the nitrogen concentration in the water body, enabling the water body to achieve ecological balance and achieve the purpose of fertilizing the water.