1. The density of the fish is high, the amount of bait is large, the scale glue on the fish body is also peeled off, and the excretion after feeding is more. This kind of foam is relatively small. 2. A large number of dead fish or live bait died (not found but left in a corner or dark place), and they have begun to rot and smell badly, and there is a carrion smell in the water. This kind of bubble is relatively large, but it can be of various sizes. 3. Feeding fish meal bait products, because the bait scattered and polluted the water quality or excessive use of gelatin, carboxymethyl cellulose and other coagulants in the bait caused the viscosity of the water to increase; it may also be because the pellets were not eaten by the fish. It deteriorates and causes water pollution. This kind of foam is relatively large, accompanied by a few large bubbles. The cause and treatment of foam on the surface of the fish tank 4. Feeding a large number of daphnia, especially large daphnia, some of the daphnia decompose after death. This kind of foam is medium and small. 5. Due to the acute death of water worms (caused by bacteria). The water is extremely turbid, and the foam is generally small, so it should be cleaned out or the tank in time. 6. Oily foods cause high water surface tension and poor permeability. 7. If you don't pay attention during the breeding period, part of the eggs discharged by the broodstock will be eaten by the fish and the other part will be left in the corner or flow into the filter tank. After a long time, it will become moldy and corrupt.