It is not mandatory to place aquatic plants in a koi aquarium, but some can be added in an appropriate amount.
Koi have relatively high environmental requirements. They consume a large amount of oxygen and are prone to the growth of bacteria. Growing aquatic plants in the fish tank will increase the consumption of oxygen. Meanwhile, the growth of aquatic plants requires oxygen and releases carbon dioxide, which may lead to a lack of oxygen for the koi. In addition, aquatic plants are likely to breed bacteria, increasing the risk of koi getting sick. Therefore, it is recommended that koi be raised in a bare tank without planting aquatic plants.
If you do want to place aquatic plants in the aquarium, you can choose some suitable types of aquatic plants. For example, floating aquatic plants like Ceratophyllum demersum and Eleocharis acicularis. These plants are not easily eaten by koi and have stable growth. Besides, some easy-to-care-for plants like Dracaena sanderiana can also be placed in an appropriate amount.
In conclusion, although it is not necessary, some aquatic plants can be placed in a koi aquarium in an appropriate amount. However, it is necessary to pay attention to choosing suitable types of aquatic plants and ensure sufficient oxygen in the fish tank to maintain the health of the koi.