What is the best way to add CO2 to an aquarium?

Carbon dioxide is very important for aquarium planted tank. Due to the geographical location, the limitation of the space in the home, and the budget of the air source cost, everyone chooses differently. It seems that the larger the capacity of the inflatable type, the more cost-effective it is. What is the best way to add co2 to an aquarium?

1. A pressurized CO2 system

2. Refill co2 cylinder 1L

3. Refill co2 cylinder 2L

4. Refill co2 cylinder 4L

5. Refill co2 cylinder 8L

6. Chemical reactor diy co2 generator 1L

7. Chemical reactor diy co2 generator 2L

8. Chemical reactor diy co2 generator 4L

9. Chemical reactor diy co2 generator 6L

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