1. The density of fish farming is too high, feeding is too much, and goldfish eat more Dora, which pollutes the water quality.

2. Sunlight or long-term illumination will make algae grow in the water, and fish manure is a good fertilizer. The longer the algae grow, the greener the water will be. Even with new water, the water turned green again a day later.

3. If the filtration is not enough, don't use the one that is filtered at the bottom of the water. It is best to use the kind circulating outside, so that dirty things can be separated from water and the filter layer can be washed every time you feel dirty.

4. Before fish farming, the water quality was not well cultivated and nitrifying bacteria did not reproduce.

Give you a solution: (it may take several days to get results)

1. From now on, you suck the fish in the bottom sand with a straw every day, and you should pound it while sucking.

2. You have to change half of the water every day. The fresh water must be kept for 3-4 days before it can be used, and kept at a similar temperature, otherwise the fish can't stand it. When the water is clean, it only takes 5-7 days to change 1/3.

3. Replace it with an external circulating filter to ensure that the stolen goods sucked in do not flow back into the fish tank.

4. Every time you change water to release nitrifying bacteria, you should also release lichen. Both of these things are sold in the market. It doesn't matter if you put too much nitrifying bacteria, but you must follow the instructions, because it is toxic, and if it is too much, it will kill the fish, but algae removal is really good.

According to the above practice, changing 1-2 weeks in a row is estimated to be clean, but you should be careful not to feed too much, because they eat too much and the water is easy to mix. Also, don't let the fish tank bask in the sun. Just keep the fresh water you changed, otherwise algae will grow in the water, which will turn your water into green water again, usually nitrate.