The co2 will come out as a bubble from your source. As you suggest, it will be sucked into the pump and dissolved into the water. go through the filter and released back into the tank.
There is not enough time for the co2 bubble to dissolve. As mentioned, the co2 bubble will damage the pump impeller in the long run. Meanwhile it will simply escape into the atmosphere when it is dumped on the filter bed of your OHF.
|