Canister filter as CO2 reactor (actual experience)

[erwin123]

My Qanvee inline diffuser got clogged and I was unable to unclog it using bleach. I have ordered a replacement ceramic part and it will take several days to arrive.

So out of necessity, I got to find out how effective an in-tank diffuser placed under the filter inlet is for CO2 mixing.

For reference my setup is:

• 90P Tank. Fluval 307 + Fluval 407
• Twinstar / Neo Aquario Medium CO2 diffuser under each filter inlet.
• Increased bubble count by 50% over previous bubble count. (about 3 bps into 407, 1 bps into 307 - caveat -bps here is useful only to compare the CO2 I'm feeding into each canister, not for comparison with other aquariums)
• Able to maintain 1.3pH drop (vs degassed pH) with far less CO2 mist

Conclusion - since I am still seeing 1.3pH drop, albeit at the 'cost' of 50% moreCO2 usage (or more technically wastage) because I can see large bubbles occasionally coming out of the filter outlet which is 'wasted' CO2, it suggests that the canister filters are sort of acting as reactors to mix the CO2. As for the 307 filter outlet, since its only running at 1bps, I don't see any bubbles or mist coming out so I presume the CO2 is dissolving.

Once my Qanvee ceramic insert is delivered, I'll revert to an inline filter for my 407, while the 307 gets fed 1bps of CO2, because Tom Barr said somewhere that plants can utilise the CO2 mist, and the mist is nearly invisible in my tank due to the lit background.