Can I add the carbon dioxide (CO2) to the suction nozzle of the external filter?
It is not advisable to add the carbon dioxide (CO2) to the tank water via the suction side of an external filter such as the JBL CristalProfi. This is better done via the discharge side with an inline diffuser, such as the JBL ProFlora direct.
The following disadvantages arise when adding CO2 via the suction side:
1) There is always a slight vacuum when the filter is running, so that outgassing of the CO2 may occur.
2) The undissolved gas bubbles collect in the impeller housing, which may lead to running noise.
3) There is also a risk of the water flow stalling in the impeller housing, which may cause a loss of function in the filter.
4) The start button is impaired when the filter is put into operation.