1. Take a bottle of water from a pond or fish pond with a good ecological environment and pour it into a fish tank.
2. When tap water is used, it needs to be placed outdoors to allow chlorine in it to volatilize, so as to avoid harm to plankton.
3. Change the water regularly, and be careful every time to avoid dumping plankton.
4. If the fish tank is large enough, a small ecosystem can be established, including sediments, plants, shrimps and crabs, fish and plankton. This will allow plankton to grow naturally in the ecosystem.
5. If the fish tank is small, you can soak the soil with water, filter out clear liquid and mix it into the fish tank to increase nutrition and promote the growth of plankton.
The above methods are for reference only and should be selected according to the actual situation and local climate, water quality and other conditions.