Sera CO2 Start - Seven Fishes

Sera CO2 Start

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Carbon dioxide (CO2) is the basic plant nutrient and allows adjusting a slightly acidic pH value, as it is preferred by many plants and fish.

The sera CO2-Start fertilizer system is easy to install and operate. It is ideal for the very widespread and popular smaller aquariums up to approx. 120 liters (31.8 US gal.). sera CO2-Start consists of an optically unobtrusive sera CO2 diffusion reactor and the corresponding sera CO2-Tabs plus.

This convenient and uncomplicated CO2 fertilization system can be integrated into the aquarium even by beginners without any previous knowledge entirely without any problems.


  1. Position the sera CO2 diffusion reactor in an area of constant water movement, for example close to the filter outlet.
  2. Attach the sera CO2 diffusion reactor (single vent at the top end) to the aquarium glass using the suction cups.  The upper edge of the reactor should be placed near the water surface (ideally 5 mm / 0.2 in. below the water surface).
  3. Then push the rubber stopper, while twisting it lightly, about 7 – 8 mm (0.3 in.) into the vent. There will be air inside the sera CO2 diffusion reactor after the weekly partial water changes. This air can escape when removing the rubber stopper briefly, and the reactor will be ready to use again.
  4. Use the sera CO2 diffusion reactor only if sufficient filtration and water agitation are provided.

The CO2 requirement depends on many factors such as lighting duration and intensity, type of planting, water current and many more.

A basic rule is:

Water Volume


45 – 60 liters (12 – 16 US gal.) 


1 sera CO2-Tabs plus every 3rd – 4th day

60 – 90 liters (16 – 24 US gal.)


1 sera CO2-Tabs plus every 2nd – 3rd day

90 – 120 liters (24 – 31.7 US gal.)


1 sera CO2-Tabs plus every 2nd day