1. must nitrifying bacteria be added to change the filter cotton? It is not necessary to add nitrifying bacteria to

change the filter cotton. There are indeed a lot of nitrifying bacteria on the filter cotton, which will cause the ecological balance in the tank to be broken after replacement, but as long as there are filter materials such as bacterial houses in the tank, the nitrifying bacteria will still exist, and the number will soon be restored, so there is no need to start culture again. It should be noted that when changing the filter cotton, do not clean or replace the biological filter material.

Synthetic fiber material: Synthetic fiber material is the best filter cotton material. Compared with other materials, it not only has small resistance, light weight, but also has large capacity and environmental protection. The price is also moderate. It is resistant to sunlight and friction, and has a certain resistance to weak acids and bases.

2. Non-woven fabric: Non-woven fabric is a filter cotton material that is widely used at present. Because it has to go through the process of making, its quality is very stable. At the same time, it has good moisture resistance and long service life. It is relatively durable. It is also the mainstream material at present.

3. Sponge: Sponge is rarely used as filter cotton. Although it can filter the dust in the air, it can prevent the water flow to a certain extent, which will affect the overall filtering effect. Therefore, it is rarely used as filter cotton inside the fish tank, which can only play a dust-proof role.