# CO2 levels too high...



## keymastr (May 25, 2015)

Yeah, I have been worried about the same thing lately. My PH in de-gassed water is 8.3 and with co2 it is 7.0. Since I am using DIY co2 I can't really turn it down. What I have done is adjust one of my filter outlets to get a bit of surface movement and at least it should be getting more o2. It has not done much to lower the co2 level but the fish are not acting weird anymore. 

In my case I recently moved some Bosemani rainbows out of that tank due to them growing too big and since then my SAE has become a real bully. I think he is the reason that my Flame tetras have been hiding since he chases them around. And the other day I was freaked out because he was real pale and just laying around. Happened again yesterday and when I did a little pruning he perked right up and displayed his colors so I think that most of what I was observing was just power struggle and the fish are just re-establishing their territory. I think I should be safe from the gassing point by a fair margin. I estimate around 30 PPM and I think the danger point is closer to 40.


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## klibs (May 1, 2014)

It would not surprise me if I had 40ppm in my tank. I luckily run my CO2 levels off of a pH controller so I can fine tune it pretty well.

Hopefully someone can chime in... I really just need confidence that my tank at 40ppm will be just as stable as my tank with 20-30ppm CO2


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## bsantucci (Sep 30, 2013)

I recently noted the same thing wiht my fish. Tank would go from 7.3 down to 5.95 each day. They were doing great when I ran my sump but I switched away to canister again and should have fixed my co2 to match.

I saw bad coloring on my rams and lethargy from them. Bumped the bottom pH to 6.15 and everything is great again. I had no issues with algae or anything else. I also run an apex in the same way you do.

If you want to play it safe, lower your light levels when you make the change, then slowly raise them again.


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## klibs (May 1, 2014)

That's what I wanted to hear. Thank you! I will slowly bump up my CO2 by like 0.02 per day until I no longer see signs of stress. It's not like I'm losing livestock - they are just unhappy. Same thing as you - poor coloration and lethargic.

The funny thing for me is that 90% of my rummys are totally fine and only like 2 or 3 are really hurting from this.


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## chinaboy1021 (May 30, 2003)

I'm having this issue also. I only have several serpae tetras in a 75 gallon (very heavily planted - jungle style) and the tetras are not active. They are also sometimes swimming at an angle. These fish had previously been super active and always hungry.

That said - we need to tone co2 down without hurting the healthy plant growth. I think we need to keep an eye out on our lighting. Might need to lower the light to match decreasing co2 levels.


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## bsantucci (Sep 30, 2013)

klibs said:


> That's what I wanted to hear. Thank you! I will slowly bump up my CO2 by like 0.02 per day until I no longer see signs of stress. It's not like I'm losing livestock - they are just unhappy. Same thing as you - poor coloration and lethargic.
> 
> The funny thing for me is that 90% of my rummys are totally fine and only like 2 or 3 are really hurting from this.


Yep, the rest of my fish in my tank were fine too, otos, corys, apistos, etc. You're playing it safer than I did. I just bumped it all at once. Also changed from BML regular lights to MC lights at the same time, so had to alter my lighting levels on the fly. All in all, worked out fine. In fact, I bumped my phosphate dosing up at the same time and in the end I got rid of all GSA on top of having happier fish and healthy plants.


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## klibs (May 1, 2014)

lol I tend to do the same thing. Make a bunch of changes at once based on what I believe is the best route to go. Can definitely end badly if you aren't 100% correct!

I'll try to play this one safe and see how it goes. Thanks again


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## Audionut (Apr 24, 2015)

CO2 contribution to plant growth is a logarithmic scale. If you reduce CO2 concentration from 40ppm to 30ppm, you don't scale back growth by 25%, more like 2%.

http://www.bio-web.dk/ole_pedersen/pdf/PlantedAquaria_2001_2_22.pdf

There's also a good post at the barr report somewhere regarding CO2 saturation.

In terms of algae, consistency is the key, not the actual level of CO2.


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## klibs (May 1, 2014)

Audionut said:


> CO2 contribution to plant growth is a logarithmic scale. If you reduce CO2 concentration from 40ppm to 30ppm, you don't scale back growth by 25%, more like 2%.
> 
> http://www.bio-web.dk/ole_pedersen/pdf/PlantedAquaria_2001_2_22.pdf
> 
> ...


Perfect - this is what I assumed was the case. Thank you for the info!


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## prp427 (Jun 28, 2011)

Another issue you may consider is better oxygen exchange via increased surface agitation. 

I have a similar setup as you (Apex controller). I was pushing almost a 1 point decrease in ph. The existing fish were doing fine. Added some rummynoses and cardinals. The weaker ones couldn't handle it and perished. I was bummed. Since then I cut the ph decrease in half and increased the surface agitation. The plants are still exploding in growth and there is minuscule amounts of algae. I'm convinced I still need more agitation before I increase the co2.


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## mistergreen (Dec 9, 2006)

Light intensity drives plant growth. Lower the CO2, lower the PAR or PUR and you should be fine with no algae issue.


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## Audionut (Apr 24, 2015)

prp427 said:


> Another issue you may consider is better oxygen exchange via increased surface agitation.


If you think you have enough agitation, you don't. :tongue:
Far better to skim the DOC's from the surface, but that's another story.



mistergreen said:


> Light intensity drives plant growth. Lower the CO2, lower the PAR or PUR and you should be fine with no algae issue.


Light is also on a logarithmic scale, however plants can utilize significant amounts of light well in excess of the levels we can control in an aquarium. Since we are already far away from the light saturation point, reduction in light can cause a significant reduction in growth.

Where CO2 concentration is near saturation for growth, reducing CO2 concentration will only reduce growth by a small margin. Look at some graphs in the PDF I linked. As CO2 is increased above equilibrium with the atmosphere growth rate is increased exponentially. However, as CO2 concentration reaches saturation (actually quite a bit before saturation), growth levels tapper off.

Increase CO2 concentration from 3ppm to 20ppm and the growth rate will increase significantly. Increase CO2 concentration from 20ppm to 40ppm, and the growth rate only increases slightly. This allows some margin of error. So for those of us who like to push things to the limit, we can actually reduce CO2 concentration somewhat, suffer little reduction in growth rates of the aquarium, and make life more comfortable for other inhabitants.

Reducing both CO2 and light will reduce growth significantly, which is probably not the outcome those with excess CO2 supply desire.

Algae adapt to changes in CO2 concentration far quicker then plants are able to adapt. We don't set CO2 concentration to control algae, we set CO2 concentration for optimum plant growth, since it's healthy plant growth that reduces the ability of algae to thrive. Once we have our desired CO2 level, it's all about maintaining consistency. It's also important to remember that CO2 concentration has a direct relationship with carbonate levels, so to maintain consistent CO2 levels in the aquarium, pH alone is not a sufficient indicator (actually it's an ok indicator, but requires careful monitoring which rules out pH controlled CO2 injection), one must also monitor carbonate concentration. If you have some substrate that reduces carbonate concentration, then it is also reducing CO2 concentration for the same pH. 

In this case, with a water change the aquarium has some specific carbonate level, over time the carbonate level is reduced, _which also reduces CO2 concentration for the same pH_. Next week with another water change, carbonate levels are increased, _which also increases CO2 concentration for the same pH_.

Bouncing CO2 concentrations for the same pH, which provides conditions more suitable for algae then plants. In this specific example, a carbonate source added to the aquarium (small amount of shell grit, or whatever), will offset carbonate loss and help to maintain consistent CO2 concentrations even during water changes.


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## mistergreen (Dec 9, 2006)

Light drive algae too.

Going from 40 to 30 ppm without reducing light is asking for Blackbeard algae from personal experience. Those that have or had it knows 😃


Sent from my iPad using Tapatalk HD


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## PortalMasteryRy (Oct 16, 2012)

The best way is to observe plant growth and see if you get the same results reducing the C02. If you want the best of both worlds then run an airstone and increase the C02 injection to match the current PH drop. That way you have high 02 levels with good amount of c02. 

I do this with my tank but I use an HOB that creates agitation.


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## Audionut (Apr 24, 2015)

mistergreen said:


> Going from 40 to 30 ppm without reducing light is asking for Blackbeard algae from personal experience. Those that have or had it knows ��


Unless your personal experience was conducted with proper due care, it's not worth that much I'm afraid.

You haven't even listed what PAR we should be reducing too. If we only light the tank with 20 PAR, should we reduce PAR when reducing CO2 concentration from 40ppm to 30ppm?

Or does your blanket statement only occur when going from a specific PAR to some other specific PAR? And if so, what!

Swap PAR for duration if that suits better.

Your statement is really no better then those who say phosphates cause algae. Sure, reducing phosphates is a method that may reduce algae, but with further research, we know that it's an ass backwards way of reducing algae.

Reducing light will reduce algae too, no doubt about it. Reducing the growth rate of plants by a significant amount is probably an ass backwards way of reducing algae also.

There are factors in algae growth that no one yet understands, defiently not this (me) clueless idiot.


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## keymastr (May 25, 2015)

Wow, that is a bit of a hostile response. Not sure that kind of post is going to be too well received.


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## burr740 (Feb 19, 2014)

Blanket statement or not, up and down co2 levels will cause algae quicker than a cat can lick it's behind. Anyone who doesnt believe that should just try it and see. :red_mouth


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## Audionut (Apr 24, 2015)

keymastr said:


> Wow, that is a bit of a hostile response.


I allowed my frustration with the amount of bull[censored][censored][censored][censored] perpetrated in this industry to effect my writing style. No ones perfect. :tongue:



burr740 said:


> Blanket statement or not, up and down co2 levels will cause algae quicker than a cat can lick it's behind. Anyone who doesnt believe that should just try it and see. :red_mouth


You sir receive bonus points for following the subject at hand. Allow me to place the pertinent points in bullet point form.



Yes, varying CO2 concentrations suit algae better then plants.
That's not the topic at hand (reread the last page).
Reducing CO2 concentration from 100% plant saturation to 96% plant saturation (say 40ppm to 30ppm) reduces growth rate only marginally.
30ppm of CO2 is above the saturation point of some plant species.
The CO2 concentration in water reduces 25% (40ppm to 30ppm), but the growth rate reduces by some significantly less margin.
CO2 contribution to plant growth is not linear, it's logarithmic.
Reducing CO2 concentration from 40ppm to 30ppm requires a reduction in light, else BBA will thrive.

The last point is the current topic at hand. :wink:


In case anyone is left wondering, I'm not here to stroke egos, play nice, make lots of friends or parrot false information. I'm here to have discussion around subjects with people who hopefully know more then I do, so that I can increase my understanding (which will lead to better conditions in my tanks), and hopefully I can impart knowledge to others. My writing style is to the point, and doesn't consider the emotional stability of those who I respond to. If this upsets the apple cart, I leave that for the community to decide judgement.


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## FlyingHellFish (Nov 5, 2011)

Audionut said:


> My writing style is to the point, and doesn't consider the emotional stability of those who I respond to. If this upsets the apple cart, I leave that for the community to decide judgement.


Haha that ok, we're all adults here. Some people's writing style are more direct, don't sweat it. I seen, read and written worse on forums.


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## Hoppy (Dec 24, 2005)

burr740 said:


> Blanket statement or not, up and down co2 levels will cause algae quicker than a cat can lick it's behind. Anyone who doesnt believe that should just try it and see. :red_mouth


One fairly common demonstration of the effect of fluctuating CO2 levels is the experience of using DIY (yeast) CO2 with more than low light. I tried it and was very pleased with the faster, more attractive plant growth. But, after a few weeks BBA visited my tank, and quickly homesteaded it. It is extremely difficult to get constant CO2 concentration using DIY CO2, and doing it week after week is beyond my abilities. So, I gave up on DIY CO2 and shifted to Excel.

Now, I have also had a couple of cats over the past years, and I never thought to compare their efforts at cleanliness to my algae problems. Just one more of an endless list of experiments that need to be done.:tongue:


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## keymastr (May 25, 2015)

I have so far managed to keep my DIY co2 going very consistently this time, however I was not able to do so before and was against it for a few years. This time is so different that I once again am a proponent.


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## Audionut (Apr 24, 2015)

I tried baking soda + citric acid. The only thing it done was expedite the purchase of pressurized bottles, regulators.............

I much prefer DIY, but this was something that was beyond my skill set.


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## klibs (May 1, 2014)

Well I have bumped my CO2 limit from 6.6 - 6.75 since starting this thread. About .02 a day. I have left the light alone which is still quite high levels.

The lone rummy that used to hide all the time is showing signs of improvement - he comes out and joins the school most of the time. He is still less colorful than the others but hopefully in time that will change.

I agree that lowering CO2 down to 30ppm-ish levels does not affect plant growth much at all. The most I am seeing is a tiny bit of green dust on my glass in a few places but this is something I had to scrape off every few weeks anyways and it's about that time. Not so convinced that the lowered CO2 caused that.

Not seeing any new BBA either. My tank used to have a somewhat decent amount of BBA in the hairgrass and hardscape but it is continuing to subside. My rotala / ludwigia / blyxa stems are still very healthy, growing quickly, and are still 95% algae free.

So I guess I disagree with the statement that someone made saying that if I don't reduce my lighting then I will get BBA. Again, I agree with burr in saying that if you take changes like this slow and don't go overboard then you will be fine. However, I do think that if I had made this change entirely overnight then I would be looking at a nice algae bloom one morning.

I'll let you guys know how it goes when more time has passed.


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