I have my 120g up and running, and wanted opinions on how to best maximize the CO2 fertilization. I currently have pressurized CO2 going into an old dupla reactor as my only CO2 injection. After reading many of the posts here and at APC, it seems obvious (even to me ) that I should introduce CO2 misting as part of the CO2 regiment.

My current setup has an Eheim 2213 pushing water through the reactor. It's not a large flow of water but seems about right given that CO2 never overwhelms the reactor. (CO2 volume in reactor seems to fluctuate between 30-75% of reactor). I also have one of the bigger Eheim profession filters pushing water from the far end of the tank in the hopes of maximizing the CO2 mix.

My current thinking is that I will add misting in addition to my reactor. For the misting, I am not sure whether to go with Tom's internal venturi reactor or something like a Rhinox (5000?). So.. thoughts?
Will

As good as Tom's reactor is, it isn't a thing of beauty in the tank. The glass ceramic disc diffusers are things of beauty. So, I think it is a matter of personal choice - do esthetics make the difference for you?

You need a lot more flow through the CO2 system if it's an external method.
You can also use a mazzii venturi valve.
That will require about 400GPH or so, and you need at least that much pushing the CO2 around.

For a 120 gallon tank 600GPH's of canister filtering is needed.
With some of the larger filters, you may be able to drive a venturi.
If not, use the disc and place near the out flow of the filter blasting the mist downward and the length of the of the tank.

Regards,
Tom Barr

Holy crap batman!?!? 600gph? I already have, in addition to the 2213, an Eheim 2028 for filtration and a rio 180 for add'l water circulation. Water seems to be moving around quite nicely. Are you concerned that the flow rate through the reactor is insufficient to absorb enough CO2?

I do have a redsea CO2 indicator at the opposite end of the tank from the reactor and its showing yellow (but that's using tank water in the indicator - have some 4dKH coming from Bill). My plan was to put the diffuser such that the rio would blow the mist around the tank. I'm not arguing Tom , but just want to make sure I understand. I have read many posts where you state that CO2 levels are often too low which is why I want to make sure I get this right.

If I do need to go 600GPH, I will definitely consider the venturi approach and hook it to an external water pump. Not sure I can justify to my financial analyst the $$$ required to purchase a canister filter that big unless folks here have recommendations for reasonably priced canisters in this range.

--Will

120 gallon tank?

Yes, you need say 400gph going through the CO2 reactor there.
The tank should have about 800-1400gph total mixing.

Realize that the plant beds reduce flow by about 50-90% inside the beds.

Regards,
Tom Barr