CO2 24/7 - Why Isn't It Done More?

Roan Art

Roan Art

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Oct 7, 2005
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One of the things that concerns me about CO2 injection are the pH swings. I have my CO2 tanks on a timer and currently my Boesemani tank shifts from 7.4 at night to 6.6 during the day. That's quite a drop. Not only that, but it takes a while for the swing to complete, so my plants aren't getting the full benefit of the CO2 I'm socking in there. My lights come on at 7:30am and go off at 7pm. My pH isn't at it's lowest of 6.6 until around 2-3pm, so that only gives me 4 hours of 35ppm. I don't even LIKE it at 35ppm, I want it at a steady 20-25ppm, but I have it at 35ppm so that they get more hours of at least 20ppm.

I think that works out to about a .2 drop per hour, is this what everyone else pretty much gets?

Another point of note is that my buffered KH shifts as well.

Now, Len posted in another thread that he leaves his running all the time and only has a .2 shift in TOTAL. To me that's a *heck* of a lot better than dropping from 7.4 at night to 6.6! I decided to run some tests on my new tank and left the CO2 off the timer and running for three days. Note that I don't have the CO2 running "full" yet. This regulator has a very touchy needle valve and it's very hard to get it to stay anywhere.

With the Timer:
Night Time pH: 7.4
KH 4.0
5ppm

Day Time pH: 6.8
KH 5.0
24ppm

Without the Timer:
Night Time pH: 6.8
KH 5.0
24ppm overnight

Day Time pH: 7.0
KH 5.0
15ppm During day

Now, my questions are thus:

1.) If one leaves the CO2 running overnight then there is very little shift to attain the desired CO2 levels. Therefore the plants get MANY more hours of optimal CO2. Based on this, if one runs a 24 hour CO2 delivery system, can the target CO2 level be lower than on a 12 hour CO2 system? In other words, instead of a target of 20ppm, of which the plants (on my tanks, anyhow) only get about 4 hours, can one's target not be 15ppm, which would be consistant at close to 10 hours?

2.) If running 24/7 and an airstone is set on a timer to gas off the CO2 build up at night, would that not help to keep the pH closer to the day time pH and therefore result in an even less pH shift of .2?

3.) Why don't more people do this? Most of what I read here and everywhere else advocates putting the CO2 on a timer. Why? Unless I'm a total moron (hey, it's possible :D ) this is a far superior method of delivering constant CO2 with minimal shifts in pH. This means less stress for the fish.

I'll probably think of more questions later.

Roan
 
I leave mine running,its a hagen yeast c02.
Good thing about it is that in the night the temp goes down in the house,so the c02 rate drops and then when morning comes the house temp goes up,the c02 rate comes back full steam...My PH levels are 6.6 all the time.
Dont know about the summer,may have to let a airstone run,have to see.

My father turns his gas off at night and it takes to midday to get the co2 levels back up,so your right,there is a few hours without good levels,mind you his tanks always look good,so he dont care.

25 gallon planted
3 wpg
c02 diy
Substrate: Flourite
Fertilization: kent grow for K and mircos
ph 6.6
kh 3
Plants..java fern,java moss,crypt becketii,Alternanthera Reineckii,wisteria
 
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Roan Art,
I leave my Co2 running 24x7. The lights are on timers the Co2 is not.

With the controller i get a shift of .2 in pH theory. In actuality the swing is more like .28. The probe is located far enough away from the return that it shuts off the Co2 when it senses the desired level "low" level.. the pH continues to fall, another .08, as the Co2 "in the system" is carried from the reactor into the tank. At the same time it takes a little bit of time for the Co2 near the return to saturate the water near the probe. the .28 swings take hours to occur on the up and down side of the equation. It took some time to get the regulator "right" where i wanted it. But, it did happen. It is gentle pH waves as opposed to spikes.

I had an air pump hooked into the controller at first. I discontinued that because it did not seem neccessary to contain the .08 drop past "target" on the low end of the pH scale.

I screwed up one night and blasted the Co2 into the tank for 10 minutes (i went into another room to watch some of "House" with my wife when I shouldn't have) dropping pH below the test kits ability to measure. The airstone was working but it could not keep up with the problem that had occrred. I got lucky in that none of the fish died (i spent many hours that night nursing them--and I thought i was done with the late nights up with my sick kids--lol). I never plugged the airstone back into the controller after that. Did not seem to be worth the effort. And for the nominal .08 shift--does not seem important enough to worry about.

The regulator is "open" only with electricity. It goes to "closed" with absence of electricity. So, I don't think I am running a risk of excess Co2 at lights out time. Especially since the system kicks in a couple of times each night to keep the pH down where I want it.

As to the optimal level of Co2 at all times. They don't consume it with lights out, right? I thought the only time the Co2 level was important was when it is being consumed. I did not know there was an optimal Co2 level at night. If that suppostition is true I would guess the only downside for the types of pH swings you mention is for the fish. That is why i am keeping the system going all night.

Using the KH/pH table I target the Co2 level for 26 ppm's. I had algae issues (like everybody else) as I started. I bumped the Co2 level to something a bit over 30 ppm's. The algae basically vanished. (hair came back a bit as i dosed the "iron" additive in search of a better "red" in some plants).
 
I agree with keeping the CO2 on 24/7. I have read articles about both methods and it makes sense to me (and experience with CO2 so far) that the pH will shift much more by turning the CO2 then leaving it on. I think the CO2 gasses off quicker when the CO2 is turned off at night than the build-up saturation occurs of leaving it on all the time. I don't bother with a pH controller because I don't touch my CO2 tank at all (except to fill it). So in theory, the pH should rise and drop the same everyday (within tolerances).

I do have a question for someone other people though:

I am running about 2 bubbles of CO2 a second and it's being diffused into my cannister. I know it is working because my Italian Val are growing like CRAZY, but my amazon swords are suffering greatly. I know I have enough light and I think I have enough fertilizers, but my amazon swords seem to be the only plant (out of the 5 or 6 species I have in the tank) that is suffering.
 
Roan, a suggestion. Set your CO2 for a lights on ppm that you are comfortable with and will give you the max.(lowest) safe pH and forget about it.
If you have a decent needle valve, you will not have to touch anything and the fish will adjust just fine.
The only downside to running the gas 24/7 is that you use it up twice as fast. So, in my case instead of refilling every 8 - 10 months, I refill at about 6 months at $15 a pop. I consider this very little for the degree of good it does for my plants.
And I refill 3 tanks!!! :)

Len
 
Len, I've read that 24/7 CO2 can cause stress on the fish at night because the plants are using O2 at night and the water can get saturated w/CO2. Is this another fable? That's why I've been turning it off at night.

Mark
 
While AC was down I spent a lot of time reading stuff at PlantedTank.net and the Barr Report.

Most of the "gurus" on those sites do not run CO2 24/7. In summary, they don't feel it is necessary and that pH swings caused by CO2 injection are not the same as swings caused by other means and are not harmful to the fish. I haven't yet surmised where they get this information from. Does anyone know?

I have found out -- and almost lost my fish in the process -- that the Milwaukee controller has a .2 "slip" factor. In other words, if you use it to set your bubble rate to keep your pH at the low of 6.6, it can really run anywhere between 6.4 and 6.8. This has been verified by several people on those sites, and I think here as well.

In my case, I had recalibrated the probe and set my bubble rate to match the controller at 6.6 and had been monitoring it all day with pH tests. I had the alarm set for 7.0. Everything was kosher and everything matched. For some reason -- either my needle valve is flaky or whatever or someone stomped on the floor and it opened up a bit more -- around 7pm that night and even though the controller STILL read 6.6, the pH was really at 6.4 or even lower.

It is possible I have a bad probe or controller. I don't know. All I know is that my fish almost died and I am furious. Furious at myself trying for relying on a probe to tell me my pH and and furious that this thing could be defective.

For one hour I was away from the tank putting my kids to bed. During that time the CO2 climbed to at least 70ppm and almost resulted in several dead fish. When I came downstairs they were ALL gasping at the surface big time, and one of my clowns was stuck in the thermometer cable -- barely breathing, not moving at all.

As it was, I had to quickly throw three bubble wands in the tank and rig up air pumps to gas off the CO2. I also had to herd the clown loach with a stick around the tank for 15 mins before he recovered enough to swim on his own. In one hour my fish were fine again, but that was a very scary hour.

I do not really know how high the CO2 was. I did not get a chance to grab a water sample until after I had shut the cylinder off and started gasing off the CO2. So, with a sample taken about 15-20 mins after everything was shut down and the air pumps doing their thing, I tested and got 6.4 pH and 4 dKH, which gives me about 45ppm. I suspect that it was closer to 6.2 pH, or lower.



No, I did not even consider doing a water change. IMO that would have not only taken longer, but the fish were stressed enough how it was. It was much easier and simpler to gas it off.

I am not a happy camper with Milwaukee atm. I have had to recalibrate that stupid thing three times just today! I do not have it submersed, it is above the water line. I calibrate and check and then I check every half hour. It never seems to fail that the minute the pH gets to 6.8, the controller slips and continues to read .2 higher than the pH really is.

I'm about ready to throw that thing in the trash. I am going to call Milwaukee tomorrow and scream my head off. THEN I might feel better about this.

Is the PinPoint controller any different?

You know, maybe I should be smart and just listen to people like Len. I don't need all that fancy-schmancy controller stuff at all. Just find a constant bubble rate I'm happy with and shut the dang thing off at night. End story.

Sometimes the simple things ARE the best. Right, Len? ;)

Roan
 
Errr where do I get my information?

A few places, common sense , practical experience (try it) and references at times.

My question to you is why add it at night when plants do not use it?
We add CO2 not for pH control, but to fertilize the plant, much like one might do with Trace elements/KNO3 etc.

24/7 CO2 dosing is not better nor a pH controller. Why would you want low O2 and high CO2? That's a bad combo.

I'd rather have high O2/CO2 levels(PM) and low O2/CO2 levels(AM).
My O2 levels sit about 95% right before the lights come on and the CO2 is nearly equilibrated.

I use a solenoid for turning the gas on/off and plug it into the light timer.
If you have the CO2 diffusion system set up correctly, you should be able to have 30ppm+ in about an hour or less.

This way you can add more CO2 during the day when you need it most and it also allows you to crank more in there without killing fish because every night it shuts off and degases. So there is no long term chronic effect of high CO2 bacteria, fish, fungi.

Just a relative brief 1/3-1/2 of a day where the CO2 is high, but so is the O2 level at these same times.

Now given these notions, which method do you think provides the largest margin of safety, and which method would allow you to add more CO2 when the plants use CO2 without harming anything?

It's very simple to do, just like the 24/7 method.
It's not tough to plug a powerhead or a solenoid into a light timer.

Amano is against it and told me it was "taboo in Japan".
I just always felt it added a margin of safety and allowed me to add more when it was needed most.

After using CO2 about 15 years, I've never gassed a fish.

Regards,
Tom Barr

www.BarrReport.com
 
Roan

You know, maybe I should be smart and just listen to people like Len. I don't need all that fancy-schmancy controller stuff at all. Just find a constant bubble rate I'm happy with and shut the dang thing off at night. End story.
Click to expand...

I am keenly interested in the hows and whys but, being a techno futz with my CO2 injection seems a little tedious to me. I agree with Len.



Jay
 
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:( top of page 2 of the CO2 sticky...I'm hurt Roan. j/k

So the fish and plants use O2 at night. This happens regardless of CO2 injection. If you're pushing the limits as Tom does, maybe a solenoid is a better (safer) option. I'm sure Tom has tested O2 levels at night in a fully planted tank with and w/o CO2. I don't run CO2 up that high and I don't have an overstocked tank so I'm perfectly comfortable running CO2 24/7, and with my night time O2 levels.

wesleydnunder, too much CO2 stresses fish. Yes, plants use O2 at night, not CO2. We're trying to avoid too much CO2 at night as the discussion ensues.

Tom, you remove CO2 at night...are you also removing Traces/KNO3 too? ;)

Bill
 
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