Tim Stephens wrote:
...
How long does your CO2 last before you have to dump it and mix a new batch?
...

I'm using the Hagen system with two bottles working in parallel. One is
the original bottle that came with the system. Another is a plastic
700ml Pepsi bottle. (700ml is about the same volume as the original
bottle. Looks like only Pepsi makes them.) The bottles are joined by a
2-to-1 gang valve and feed the same reactor.

I replace the mix in each bottle every 4 weeks with 2 weeks overlap
(i.e. I reload the first bottle; in two weeks I reload the second
bottle; in two more weeks I reload the first again; etc.) That helps to
both intensify and even out the CO2 production. The latter is the main
point of using two smaller bottles instead of one bigger bottle. I think
that with my setup I can even switch to 5-weeks-per-bottle cycle without
significant reduction in CO2 production.

The only problem I continuously have with my DIY setup is that white
stuff (bacteria?) that keeps accumulating in the reactor where CO2
bubbles enter the water. At first, it causes the slight increase in size
of each bubble. Later it accumulates in the bottom portion of the
reactor and causes the bubbles to get stuck in the reactor for some time
and combine with each other. Both reduce the amount of CO2 that gets to
dissolve in the water instead of escaping to atmosphere. In the severe
cases the buildup makes the bubbles to bounce and miss the reactor
completely. Removing relatively large clumps of this white stuff is not
a big problem. However, cleaning the path completely (so that the
bubbles don't get stuck at all) could be difficult and might require
removing the reactor from the tank.

I wonder if anyone knows any solution that would prevent this stuff from
forming in the reactor in the first place. What if I bubble the CO2
through an intermediate water-filled container (as suggested in many DIY
CO2 designs)? Does anyone know if it will help to fight the buildup of
this white stuff in the actual reactor?

--
Best regards,
Andrey Tarasevich