The water will turn yellow after oxytetracycline under the fish tank. If you want to make it clear again, you only need to change the water regularly. Oxytetracycline is usually administered because the fish is sick. This drug has a good therapeutic effect, but it will cause the water body to turn yellow, which can be gradually improved by changing water. If the water is still very yellow, it means that the filtration of the fish tank is not good, or the drug is overdosed. The former needs to strengthen the filtration, while the latter needs to continue to change water and control the dosage.

1. Aging of water quality: Yellowing of fish tank water is usually due to aging of water quality. The water for fish farming should be changed regularly, otherwise it will age over time, and the old water usually appears yellow and doesn't look very clear. Generally, the water should be changed every five to seven days, about a quarter of each time, so that the water quality can be maintained.

2, sunken wood yellow water: If sunken wood is placed in the fish tank, especially untreated sunken wood, it will also cause yellow water. This yellow water has little effect on fish, but it doesn't look very beautiful. Therefore, before putting the sunken wood into the fish tank, it is best to cook it in a pot, and then put it in the fish tank after several times, so that the water will not turn yellow.

3. Yellow water in feed: Some feeds contain pigments, which are not completely digested after feeding fish, and will lead to yellow water after being discharged. At this time, the best way is to change the feed and feed it with other foods, so as to avoid the yellow water.