I think that I found something that will work. I will just attach a small pieace of co2 tubing to the rigid 3/16 tube and then attach this Aquatic Micro Ball Valves for Aquariums to the other end. Should work, I think.

I recently built a DIY reactor and decided against putting the side venturi on it, just figured I'd use the top venturi. I made the 3/16" rigid tubing for the top venturi a little longer than in the original design so I could see it easily from the outside. I ran into a problem, however. Whenever I did a water change, it took a long time for the big PVC tube to fill completely, probably because the little Rio 800 pump just had too much air coming in thru the venturi tube. And, during this period, sometimes an hour or more, it was extremely noisy. Honestly, today I do not think it was going to completely fill at all ... it just kept running poorly for over an hour.

My solution: I put a 3rd hole in the top and put a piece of very short 3/16" rigid tubing into it, so it just barely came thru the top cap on the inside. I then put a short piece of air tubing onto this, so it was long enough to reach into the tank. I do not have a valve to put on the end, so I simply folded the air tubing back over itself and rubber-banded it. Now when I start up my reactor after a water change, I open up the air tubing on the 3rd hole and the reactor fills almost immediately (when water shoots into my tank, I close up the air tubing) and runs quietly from then on.

I still like using the top venturi method, so if I had to do it over again, I'd probably just put 3 holes in the top from the beginning.

Perhaps I did a poor job building my reactor, but just wanted to share this, in case someone else runs into the same problem as I did.

How did this work out for you?

I'm building a 120 gal tank and have the parts for an external reactor, which will be in the output line of a canister filter. I can loop the venturi line back into the cannister output / reactor input line w/ a "T" connector or have it feed a power head inside the tank. The advantage of the first plan is less stuff in the tank while the advantage of the second plan is more flow in the tank. I would like to hear your POV.

Another idea is to use this powerhead with a needle wheel:

Octopus Water Pumps - AquaCave

30$ and it'll fry any bubble into mist.
225gph.

You can feed CO2 directly into the powerhead and place it inside the tank.
Or add it a sump and feed the output to sump return pump.
There are likely other applications.



Regards,
Tom Barr

I have the vent valve line at the top of my external reactor connected to a powerhead in the tank, with a drilled rotor, so I get CO2 mist as well as CO2 dissolved in the water in the reactor. This isn't working well.

The problem is that the CO2 in the reactor doesn't remain there long enough for much of it to dissolve into the water, and CO2 mist is less efficient as a way of dissolving CO2, so I need to use considerably more bubbles per second to get acceptable CO2 level in the tank.

The solution will be to follow Tom's original design more closely, and take the excess CO2 from the reactor at a point lower than the top of the reactor, so a CO2 bubble stays in the reactor at the top, with the incoming water flowing through it. I haven't done this yet, since it requires carefully removing the reactor so as not to dump a lot of water on the floor, drilling the hole, and reinstalling the reactor. Soon I will try this.

A secondary problem was that I neglected to renew the solution in the drop checker for too long. That made the drop checker color be green when it shouldn't have been. It seems that the liquid needs to be replaced at least every two weeks. I'm not sure why, but the color is from a dye and dyes are notorious for gradually fading or otherwise changing color after prolonged exposure to light. Anyway, the result of this was me thinking I had good CO2 (green drop checker) when I didn't, thus masking the deficiency of my bleed valve method for connecting the "needle wheel" powerhead.

Occasionally, enough C02 accumulates at the top of the reactor to stop the flow. Currently using the Dual venturi DIY External CO2 reactor show in this thread. Also using the 2 inch from the top hole looped back to the Rio 600. Running 3-4bps on tank w/sump. Everything is sealed and DC is green 2 hours after lights on. Would using the second (3") tube at the top of the reactor change and/or degas better? The current venturi is wide open, tried regulating with small drip valve but then it locked up daily. Any thoughts?

Moved venturi to top hole next to CO2 in. WOW, I thought the misting was pretty good from the side hole, now the misting is 2, 3, maybe 4x better! unless it's because there is a fair amount of gas in the reactor right now. Will see tomorrow, might have to turn needle down a bit.

You might simply need more than a Rio 600, try a Rio 800-1000 etc, or a maxi jet 1200 etc(not as bulky).

Regards,
tom Barr

Well using the top hole didn't work either. In fact, only made it four hours before gas lock.

Will try larger pump, this is on a 30 gal. Might blow fish away. The Rio 600 when working had good current/flow.

Will let you know, thanks Tom.

Might just try the needle wheel method and use that.
Simple and will not lock.

Regards,
Tom Barr