Why do fish tanks always have bubbles?

Tap water contains organic matter with a small amount of impurities. After being in the water tank for a period of time, the oil and grease of the organic matter dissolve in the water and surface.

2. Eighty percent of the algae’s tissues are “oil lipids”. After the algae dies and decays, the oil dissolves in the water and then surfaces. When new water is injected, the grease attached to aquatic plants, tank walls, etc. will be flushed out and then surface, creating an oil film on the water surface. ?

3. Grease produced by the remains of microorganisms or old waste, residual bait, organic matter, etc. The oil film is most serious when there is no flow on the water surface. ?

4. The filter material in the filter is too dirty, causing grease to overflow.

Extended information:

Koi is also called the original species of Crimson Koi, which is red carp (Cyprinus carpio). As an ornamental fish, red carp has become very popular in the Ming Dynasty. It is said that koi carp originated from Guangxi Longzhou koi, Jiangxi Xingguo red carp, and Zhejiang Hangzhou golden carp. It was introduced to Japan from my country in the early days. After long-term artificial selection by the Japanese people, there are now more than 100 varieties.

According to literature, Japanese nobles first put koi carp in the pond for viewing. It was rare for common people to see it. In the early days, it was called "red carp", "color carp", and "flower carp". After the World War it was renamed "Koi". In 1973, as an envoy of friendship between the people of China and Japan, Japanese koi settled in our country. "Carp streamers" are also hung on Boys' Day in Japan, which shows the Japanese people's love for koi.