Insufficient oxygen in the fish tank is a common problem, how to tell if the fish tank has enough oxygen?Here are some ways to do it:1Observe fish behavior: If the fish keeps floating its head and has difficulty breathing in the water, this may be a sign of hypoxia. When there is not enough oxygen in the tank, the fish tend to exhibit some unusual behavior. They may constantly float their heads, trying to breathe more oxygen through the water's surface. In addition, fish may also have difficulty breathing in the water and show a state of nervousness. These behaviors are all manifestations of hypoxia in fish, so by observing fish behavior, we can preliminarily judge whether the fish tank has sufficient oxygen. 
2.Check the water quality: the increase of microorganisms or plankton in the water consumes a large amount of oxygen in the water, and the semi-permeable function cannot be realized, and the fish begin to lack oxygen. Water quality is one of the important factors affecting the oxygen content of a fish tank. If there are more microorganisms or plankton in the water, they will consume a lot of oxygen in the water, causing the fish to become hypoxic. In this case, you can check the water quality to see if this is the case. For example, you can observe the change in water color, smell the smell of water, etc. If the water quality deteriorates, it is necessary to replace the water in time or take other measures to improve the water quality. 3.Use aeration equipment: Aeration equipment can increase the amount of dissolved oxygen in the water quality and prevent the fish from hypoxia. Aeration equipment is one of the effective means to increase the oxygen content of fish tanks. Through the aeration equipment, more oxygen can be injected into the water to increase the amount of dissolved oxygen in the water, so as to ensure that the fish do not suffer from hypoxia. When using aeration equipment, it is necessary to pay attention to issues such as power and noise of the equipment to avoid unnecessary interference to the fish. 
4.Control the feeding density: If the feeding density is too large, the oxygen in the water will not be enough, and the needs of all the fish cannot be met. Stocking density is another important factor affecting the oxygen content of a fish tank. If the stocking density is too high, the water will not have enough oxygen to meet the needs of all the fish. Therefore, it is necessary to pay attention to controlling the stocking density and avoiding overcrowding when raising fish. 5.Clean the filter regularly: Faulty filters can lead to insufficient water circulation, affecting water quality and oxygen flow. The filter is one of the important equipment in the fish tank, which can effectively remove impurities and harmful substances in the water. However, if the filter fails or is not cleaned for a long time, it can lead to insufficient water circulation, affecting water quality and oxygen flow. Therefore, the filter needs to be cleaned regularly to keep it functioning properly and good filtration. 
In summary, it is necessary to consider factors such as fish behavior, water quality, aeration equipment and feeding density to determine whether the fish tank is sufficient. If necessary, the filter can be cleaned regularly to keep the water clean.