03/09/2026
We run high CO2 levels in many of our aquariums, and a common question is how to avoid gassing fish. The key is good gas exchange: keep the water surface clean and ensure surface water circulates with the deeper layers. You can achieve this by placing outflows near the surface and using surface skimmers to keep the surface clear.
The mechanics of CO2 injection can feel counterintuitive to beginners. Many think that minimizing surface agitation will maximize CO2 in the water, but this can cause CO2 to build up too quickly. High CO2 saturation in the water column needs to be paired with strong off-gassing so the system stabilizes at a high equilibrium point. Good gas exchange is the key to avoiding gassing fish.
Tank grown with:
APT Feast aquasoil
APTe