# Tragic CO2 experience



## Tom Higgs (Mar 2, 2006)

AFter months of waiting to get the time, I finally got my compressed CO2 up and running. I built one of the DIY reactors. Yesterday around 1pm I got it up an running. I watched it closely throughout the day until late at night and everything seemed ok. I noticed that I had to keep bumping up the amt. of CO2 to get it to about 1 bubble / min or less, not sure if I was getting back pressure or something in the reactor. I have it on timed solenoid, and when I checked it this morning, no CO2 was coming out as expected. I tweaked my timer a little to kick it on a little early, as I was leaving for the day and wanted to make sure everything would work right while I was gone. There was a lot of initial bubbling, but within a minute or so it was down to about 1-2 bubbles / min. and was slowing down so I thought I was fine. When I came back about 12hrs later ALL of my fish were dead and the 5lb tank was completely empty. The pH was below readable with my kit. I opened the hood (no one is there to jump out), so while I try to figure out what happened I'll let the CO2 dissipate. This is really heartbreaking.....I've had some of the fish for many years. 

Do the reactors generate back pressure? Could whatever caused the backpressure have broken free, then the tank just free flowed continuously. 
Regulator problem? (I'm using a Milwaukee MA957 regulator with bubble counter, needle valve and solenoid). 

Any help is appreciated.....


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## AaronT (Apr 26, 2004)

Had you just filled the CO2 tank before you set it up? They do build more pressure as they come to room temperature. If you adjusted everything while it was cold that could have been the problem. A room temperature CO2 tank operates at around 800 psi.

Also, you may not have had the tank itself all the way open. That is important or that pressure will not be stable. 

Here's how I setup that same regulator: 

Make sure the CO2 tank is open all of the way. Now adjust the pressure to about 20 psi using the large black knob. Now briefly open the needle valve a lot and close it. Does the pressure stay at 20 psi? If not, then adjust it back to 20 psi and repeat. Once the pressure holds steady then slowly adjust it to the bubble rate you want and it should work fine.


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## hoppycalif (Apr 7, 2005)

One lesson I think we all learn eventually is not to change anything on our CO2 set up unless we are going to check on it every half hour or more often to make sure it remains ok. I once killed some of my fish by increasing the bubble rate a bit, using the needle valve, then not checking back right away. The Milwaukee regulator needle valve is just barely sensitive enough to use, and it doesn't do small changes in bubble rate. I find it best to get close to an acceptable bubble rate, let it stabilize, then make the final adjustments by changing the regulator output pressure.

Another possible problem is CO2 leakage. A small leak, like we usually see, is a lot of CO2 compared to the minute amount we inject into the water. So, if that leak self-seals, such as by a seal slightly shifting, the bubble rate will go way up. 

And, my Milwaukee solenoid failed by sticking open, so I had to replace it. That means the fish were subjected to high CO2 at night with lights out, when none is needed by the plants. I didn't recognize this for quite a few days. My point is that careful watching is a good idea when using CO2.


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## oRiN999 (Apr 22, 2006)

i had almost the sameproblem with my milwakee. when you first set it make sure you set the psi to about 40 lbs if when you open the needle valve andthe psi goes down open it further until it holds 40 psi constantly then do the fine tuning with the needle valve. i fought with it for a few days too but never had it open all the way up sorry to here about your losses but it really is a good regulator i prefer it over the jbj


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## standoyo (Aug 25, 2005)

Hi,

Sorry to about your loss. It happened to me more than once so i went and buy one that has a bigger knob for fine tuning the b/ps.

Regards

Stan


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## Tom Higgs (Mar 2, 2006)

Thanks to all for the response, my thoughts are below. When your solenoid kicks on, does anyone get a large burst of CO2 which then settles down, or does it start right up at the desired rate. Just curiousl


1.) I've had the cylinder in the cabinet for about 1 month, so it had equilibrated.
2.) The cylinder was all of the way open.
3.) I set up the regulator as directed by the instructions (yeah, I know a guy follows instructions, but I really did.)...... as per those instructions the needle valve remains closed, unless you cant get the flow regulated with the main adjustment knob. They recommend an outgoing pressure of less than 10psi, or to the desired bubble rate, again using the main adjustment knob. What is interesting here is that the responses are saying to go to 20-40psi, then get the bubble rate fine tuned with the needle valve. Using the directions provided with the regulator, the pressure required to get about 1 bubble / sec was so low it never measured on the guage. Could this have been the problem? Are you all able to achieve 20-40 psi and bubble rates of about 1/sec? I thought I knew regulators, maybe I am missing something here. 
4.) I agree with watching carefully... I really wanted to hang out all day to keep an eye on it, it just wasnt possible. I had some level of comfort after about 7hrs of usage the night before, where I closely monitored the pH and flow rate..
5.) I guess leaks are always possible, but I checked it real carefully

last question: when the solenoid kicks off for the night, do you get back-flow of water into the bubble counter? 

It was amazing how fast the pH came back to normal; checked it this morning and it was back to about 7.5. The water's pretty cloudy, so I guess its water change day. I am planning on getting the cylinder refilled on Wed. and trying it again. I dont plan on getting any more fish until I get this straightened out. 

Thanks again for the help


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## BryceM (Nov 6, 2005)

Sorry about the fish.

I also have the Milwaukee combination regulator/needle valve/solenoid/bubble counter unit. The instructions that come with the thing do indeed tell you to leave the needle valve wide open while making adjustments with the regulator knob. My cheap advice........ throw the instructions away.

I'm really not sure why they suggest this, since it is a pretty risky way to operate. The needle valve is the biggest piece of insurance in the system. The large gas regulator valve is meant to supply bulk gas at a constant pressure. Making little fine adjustments like we need is best done with the needle valve. The big regulator just isn't precise enough to do this, especially with a solenoid opening and closing. I'm not at all surprised by the large burst of CO2 when the solenoid opens. 

On my system I close the regulator valve fully, open the tank valve fully, check for leaks, close the needle valve, open the regulator to provide about 4 or 5 psi, and adjust the needle valve to provide about 2 bps for a 46g tank. Once things are set up, you never need to touch the big black valve. Hoppy is right, the supplied needle valve is just barely sensitive enough to use. I'll probably modify my next installation to include a very fine pitch needle valve to allow more precise adjustement.

Leaving the needle valve wide open is also an invitation to the "end of tank dump" where the regulator sticks open and the last 5-10% of the CO2 gets dumped out all at once.

I don't ever get backflow with the solenoid closed. Also, it shouldn't be possible for you to build up pressure in the reactor. It's open to the tank on at least one end right?


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## hoppycalif (Apr 7, 2005)

One thing the Milwaukee regulator lacks is a check valve. Without a check valve you are likely to get water back flow to the bubble counter and possibly on to the regulator. You can order a good brass check valve from here: http://www.rexgrigg.com/sale.html . If you install it near the top of the CO2 line at the tank it works the best. Without it when the solenoid opens the incoming flow of CO2 has to push water back to the tank before any CO2 gets into the tank. I tried a plastic check valve from McMaster Carr's website, a good one, but it only lasted leak free for about a month.

The regulator can be used to fine tune the flow rate if you are using the needle valve to set a rate near what you want, with the regulator set at about 25-30 psi. Then you can adjust that pressure slightly with the regulator, and that adjusts the flow slightly. But, never, ever try it at only 10 psi because it can take that much just to reopen the closed check valve or to start bubbles coming out of a ceramic disc diffuser. And, the regulator isn't stable at that low a pressure.


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## Tom Higgs (Mar 2, 2006)

thanks again..
I tried to find the plans for my reactor to show you what I built, but couldnt. Its basic premise is like others I've seen: water flowing into a 1.5 inch PVC pipe filled with bioballs. The gas enters near the bottom of the column so it wants to go up the column against the water flow. With the flow rate and bioballs there must be enough turbulance to be pretty effecient. I'll try this week to run with about 20-30psi and use the needle valve to work the flow. Hopefully I can re-populate the tank soon.... I just built the tank into a wall as part of a basement renovation, looks pretty lonely with nothing swimming around....


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## erik Loza (Feb 6, 2006)

Very sad, indeed. Perhaps for future reference: I am using your pH controller but instead of the Milwaukee velve and regulator, I use a medical-grade high/low gauge and needle valve manufactured by a company named "Cordus". It was from a hospital oxygen tank and has a VERY precise adjustment knob. I found it on ebay as part of a surplus sell-off. The O2 tank needs to be hydro'd and stamped (saved for some future tank) but I immediately put the regulator and valve onto the current CO2 tank. As others have stated, keep your tank at house temp for at least a day before hooking it up and do be around to check the progress of the new setup for several hours. Sympathies and good look with your tank.


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## carbondreams (Jun 4, 2006)

Im sorry for your loss, the same thing just happened to me. I lost almost every fish, save three bloodfin tetras I coaxed back to life. Good luck, and I would add more fish as quick as possible to keep the biofiltration from dying off.


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## Tom Higgs (Mar 2, 2006)

I have been pondering the set up of the reactor.... should the water flow be countercurrent to the rising bubbles or should they flow together down the reactor, with bubbles breaking apart on the bioballs?


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## BryceM (Nov 6, 2005)

The correct way to set up a reactor is to have the water flowing downward. The CO2 bubbles should be added about 1/3 to 1/2 way down from the top. The flow of water will tend to move the bubbles downward, and the bouyancy of the bubbles will tend to move them upward. As the bubble dissolves, its diameter will decrease to the point that it will be carried along in the current according to Stoke's law.


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## Tom Higgs (Mar 2, 2006)

thanks for the info, especially regarding NOT to follow the supplied directions. I followed the instruction you all provided and everything has been working fine for a couple of days. Added a few fish and things are back on track. Now I just have to fine tune the CO2 dosage to get to about 30ppm, and get some brown algae under control. I have it growing on my sword and anubias leaves. Any suggestions?


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