# Another CO2 Reactor



## hoppycalif (Apr 7, 2005)

This is the Tunze Reactor, https://www.amazon.com/Tunze-USA-70...UTF8&qid=1523506075&sr=8-1&keywords=Tunze+CO2 Of course we can always just buy one, but why give up an interesting DIY project??

One additional feature that could be added to this is a recycle loop, as originated by Tom Barr, for other reactors, so CO2 can't collect in the top of the tube. So, I made a sketch of how I would make one:









I found a very cheap submersible water pump on Amazon, $9 for a 80 gallon per hour pump. https://www.amazon.com/gp/product/B079HPLFBC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 
It is almost the same one I now use, so I know it is good quality for the price. And, I have some leftover acrylic tubes, including a 3/4 inch diameter one, so I will use that for the main tube. And, a trip to my LFS let me find a pack of 4 acrylic air tube connectors, which I can use for the CO2 connections. The little pump, which I got today, uses 3 tiny suction cups to hold it in place, and I found a leftover suction cup that works with 3/4 inch diameter hoses/tubes from some filter I had, and I can use that to hold the tube in place.

So, tomorrow the project fun begins!


----------



## hoppycalif (Apr 7, 2005)

The recycle port is installed, using two nesting acrylic tube pieces and acrylic glue, so there will be an area at the top where all of the gases that end up there can be sucked into the inlet of the pump.









The port for the pump outlet to enter the tube is glued into a hole at the top of the tube. The pump comes with two different outlets, so I could use the smaller one to avoid cracking the tube when I drilled the hole for it.


----------



## DutchMuch (Apr 12, 2017)

this looks like an interesting DIY project


----------



## hoppycalif (Apr 7, 2005)

The port for the incoming CO2 is a air tube connector, glued in place. (The big tube cracked, but I glued it back together.)








With the pump attached.

I'm thinking about trying it first without the recycle tube installed, just to see how much CO2 escapes from the tiny hole on top. If it is a trivial amount I won't use the recycle feature, and this will prevent a big build-up of air in the top of the tube, which would constantly cycle through the pump. Tomorrow, when all of the glue is fully hardened, I will install it and try it.


----------



## hoppycalif (Apr 7, 2005)

DutchMuch said:


> this looks like an interesting DIY project


It is almost too simple to be interesting. If it works well, that will make it very interesting! I'm out about $13, and I can always use the pump for other things if this doesn't work out well. The low cost is partly because I have a lot of surplus aquarium stuff - acrylic tubes, acrylic glue, etc.

Incidentally, the big tube is 12 inches long, and has a 5/8 inch inside diameter.


----------



## tiger15 (Apr 9, 2017)

With a 12” tube, you will not likely need the feed back loop to release the air pocket. My Tunze tube is only 7”, and I was thinking of adding an extension to increase the bps limit, if needed.

The in line reactor has no issue with air pocket, as it gets burped off periodically.

The air pocket is not just co2, but I believe it’s a mixture with nitrogen and oxygen stripped off from rising co2 bubbles. It takes hours to accumulate a sizable air pocket, and it also takes a while to dissipate after stopping co2 After I did WC, I need to flip the Tunze tube upside down to to let go the air pocket to prime the pump. So the magnet attachment is handy, but not easy with suction cups. So even though I don’t think Barr’s feed back loop is functionally necessary, having a release valve there will be handy for priming.


----------



## hoppycalif (Apr 7, 2005)

Here it is, operating, sort-of! I need about a 1 inch to 1 1/4 inch diameter tube. The water zooms down the tube so fast the CO2 bubbles are swept out the bottom, but the water flow then traps those bubbles for a minute or so, before each one gets out of the vortex and goes to the top of the tank, with some of them entering the pump inlet, to be recycled. It is working, just not like it is supposed to.


----------



## hoppycalif (Apr 7, 2005)

As odd as it seems, with the column of bubbles below the opening, it is working fine. My CO2 level quickly built up, and as about as good as I have had with this DIY CO2 set-up. I may just use it this way.

But, I did find an 8 inch length of 1 1/2 inch diameter acrylic pipe that I could try. I will probably try it just to see what the difference is. I'm almost sure it won't have the bubble column.


----------



## hoppycalif (Apr 7, 2005)

Version 2: A 8" inch long 1 1/2 inch diameter tube. I put a 1/16" hole in the top of the black cap to let any accumulated air bleed out. For now I won't use the recycle line. If I can see an advantage to it I will add it later.


----------



## mistergreen (Mar 3, 2007)

I think you can feed the CO2 into the pump's feed line. The propeller will break up the bubbles to smaller bubbles for faster diffusion.


----------



## hoppycalif (Apr 7, 2005)

[/URL] Version 2 operating in the tank. It seems to work perfectly. The CO2 bubbles rise to the top, making a big bubble of CO2, which grows very, very slowly, so most of the CO2 is dissolving in the water. After a few hours I will be able to get an idea whether I get more dissolved CO2 with this version, or less, or the same as with the first version.

The first one was more interesting to watch, but it did allow more CO2 bubbles to escape to the surface.



mistergreen said:


> I think you can feed the CO2 into the pump's feed line. The propeller will break up the bubbles to smaller bubbles for faster diffusion.


 The reason I was less happy with feeding CO2 into the pump was the CO2 mist, which is a bit distracting, and because it was difficult to see the bubble rate without diving under the tank and using a flashlight to watch the bubble counter. And, of course, I love making stuff like this! I did get a bit more CO2 dissolved with version 1, so I expect to do at least as well with this version.


----------



## tiger15 (Apr 9, 2017)

Hop, your second design looks good and more professional than your first design. A larger diameter tube allows slower velocity preventing sweeping bubbles out of the tube. I notice my Tunze reactor pump is only rated 70 gph, so apparently higher flow will not perform better. If you can locate your reactor to the lowest point, you can dissolve CO2 faster due to higher water pressure.

I use my Tunze reactor as a substitute bubble counter, as my real bubble counter underneath the cabinet is hard to read and has dried up long time ago. Another way to gauge how much CO2 is dissolving is to measure the length of air pocket building up in the tube over the same time period. If you run your DIY CO2 continuously, you need to bleed the air pocket from time to time. I run my Tunze reactor continuously and the air pocket is slowly dissipated during CO2 off period.



mistergreen said:


> I think you can feed the CO2 into the pump's feed line. The propeller will break up the bubbles to smaller bubbles for faster diffusion.


 Having a propeller to chop up bubbles may sound like a good idea, but the bubbles may chop up the propeller instead over time due to cavitation effect. I haven't tried it for a long time but experimented feeding CO2 into a power head and did not like the sand blasting sound. A reactor is designed to dissolve CO2, not to atomize it into mist.


----------



## hoppycalif (Apr 7, 2005)

tiger15 said:


> Hop, your second design looks good and more professional than your first design. A larger diameter tube allows slower velocity preventing sweeping bubbles out of the tube. I notice my Tunze reactor pump is only rated 70 gph, so apparently higher flow will not perform better. If you can locate your reactor to the lowest point, you can dissolve CO2 faster due to higher water pressure.
> 
> I use my Tunze reactor as a substitute bubble counter, as my real bubble counter underneath the cabinet is hard to read and has dried up long time ago. Another way to gauge how much CO2 is dissolving is to measure the length of air pocket building up in the tube over the same time period. If you run your DIY CO2 continuously, you need to bleed the air pocket from time to time. I run my Tunze reactor continuously and the air pocket is slowly dissipated during CO2 off period.


The 1/16 inch hole I have in the top of the tube lets the air bubble out. I get a small bubble every few seconds from that hole, and the big bubble trapped in the top of the tube doesn't ever get any bigger. It is swirled around by the water and only sheds the excess air when the bubble sits under the tiny hole long enough.


> Having a propeller to chop up bubbles may sound like a good idea, but the bubbles may chop up the propeller instead over time due to cavitation effect. I haven't tried it for a long time but experimented feeding CO2 into a power head and did not like the sand blasting sound. A reactor is designed to dissolve CO2, not to atomize it into mist.


 I have used little pumps to chop up CO2 bubbles for several years now without any problems. It works best if you drill a little hole or two in each of the rotor flappers. That method may be the optimum way to get CO2 to the plants, but you always have microscopic bubbles in the water, which eventually gets on your nerves.
I suspect the fact that the rotors are a not very hard plastic protects them from any cavitation damage.


----------



## tiger15 (Apr 9, 2017)

When you drilled holes in the propeller, will you make the rotation out of balance and create clicking noise. This happened to noisy HOB when the propeller gets worn out.

The Tunze reactor does not come with a bleeding hole. So the motor is not self priming in WC when the air pocket is locked. I have to flip the tube up side down to release the air pocket. 

The size of the air pocket will reach an equilibrium proportional to the bps . At very high bps, the air pocket will expand to the bottom of the tube signaling the limiting capacity of the reactor. The Tunze reactor dissolves 100% co2 with no misting until the capacity is reached.


----------



## hoppycalif (Apr 7, 2005)

I suspect the Tunze reactor is a better design. It costs about $60. Mine cost me $9 for the pump and $4 for a package of air tube connectors. I can buy 10 inch pieces of 1 1/2" (38 mm) diameter acrylic tube for about $7 on Ebay, or you can get a 6 foot long piece from Tap Plastics for about $24, or $4 per foot, so I could have made it for about $20 even if I didn't have a stash of scraps. And, I had a lot of fun making it!

The little bleed hole I have works perfectly!

There are many options for getting CO2 dissolved in the tank water. All of them work, some better than others.

I have drilled the rotors in several different powerheads and pumps, and none have shown any sign of problems. I try to make each blade have the same number of holes, but when I first did this I didn't even work very hard doing that. If the rotor is out of balance I suspect the solid bearings that it spins in will eventually wear too much, but I haven't seen that.


----------



## tiger15 (Apr 9, 2017)

I don't think it is necessarily a better design. It's a simple idea and you did a good job in imitating it at fraction of the cost. It's pricey because it is made in Germany, and there is no imitation I can find in Ebay.


----------

