Lots of things to consider and the bubbler is actually almost as complex as the reactor itself.
Yep, the thing I've found is that the idea and design stage is quite easy compared to the often unanticipated problems and complications that arise in actually constructing a working model.

Regarding freezing, I should imagine that dry cells are much more prone to problems due to their design. I used ordinary car anti-freeze in a wet cell I employed for a time, with seemingly no ill-effects.

I have to consider this with my new designs, but due to the fact that I will be employing cavitation and plasma discharges, I'm reluctant to use additives which under these conditions may just react unpredictably.