1.The Important Uses of CO₂ Cylinders in Miniature Aquariums:

（1）Providing a Carbon Source: Aquatic plants convert carbon dioxide and water into organic substances and oxygen through photosynthesis. In a miniature aquarium, due to the limited water volume, the content of carbon dioxide is restricted. The CO₂ cylinder can continuously and stably supply an ample carbon source to aquatic plants, promoting their photosynthesis and enabling the plants to thrive. For example, common aquatic plants like Anubias and Java Moss will grow more exuberantly and have greener leaves when supplied with sufficient carbon dioxide.

（2）Adjusting the pH Value: When CO₂ dissolves in water, it forms carbonic acid, which can moderately decrease the pH value of the water, making the water quality slightly acidic. This helps to create a water quality environment suitable for the survival of certain ornamental fish and aquatic organisms. For instance, tropical fish such as Discus fish and Tetras mostly prefer to live in slightly acidic water. By controlling the content of CO₂ in the water with a CO₂ cylinder, the pH value of the water quality can be adjusted and stabilized within an appropriate range, which is beneficial for the growth and reproduction of these organisms.

（3）Inhibiting Algae Growth: When aquatic plants obtain sufficient carbon dioxide for photosynthesis, they will grow more vigorously, thus having an advantage in competing with algae for nutrients and light. This can effectively prevent the excessive proliferation of algae, maintaining the water clarity and aesthetic appearance of the miniature aquarium. If the supply of carbon dioxide is insufficient, aquatic plants will grow poorly, and algae are likely to multiply in large numbers, affecting the viewing effect of the aquarium.

2.Determining the Appropriate Content of CO₂ in a Miniature Aquarium

1) Observing the Status of Aquatic Plants

① Growth Situation: When the content of CO₂ is appropriate, aquatic plants will exhibit a good growth state, with new leaves growing rapidly, green and glossy leaves, and upright plants. If there is insufficient CO₂, the plants may grow slowly, with yellowing and thinning leaves, and may even show albino phenomena. When there is an excessive amount of CO₂, the plants may suffer from bubble disease, with too many oxygen bubbles attached to the leaves.
② Performance of Photosynthesis: Under sufficient light conditions, observe whether the plants have obvious signs of photosynthesis, such as the generation of fine oxygen bubbles on the leaf surface. If the bubbles are evenly produced and there are many of them, it indicates that the content of CO₂ is relatively suitable and can meet the photosynthetic needs of the plants. If there are few or no bubbles, it may mean that the CO₂ is insufficient. If there are too many bubbles and the plants show abnormalities, it may indicate that the CO₂ is excessive.

2) Referring to the Status of Fish: 

If the content of CO₂ is too high, the dissolved oxygen content in the water may be relatively reduced, causing fish to exhibit phenomena such as gasping at the water surface and rapid breathing. In this case, it is necessary to appropriately reduce the supply of CO₂. On the other hand, if the content of CO₂ is too low, the fish may appear relatively quiet and less active, which may be because the aquatic plants are not growing well and cannot provide sufficient oxygen and a suitable environment.

If you are interested in the specific details of the various weights of our CO₂ cylinders, you can click the link below to learn more.