# CO2 sensitivity in Otos and shrimp



## TOO (1 Oct 2013)

Hi all,

Since introducing Otos and Amanos four weeks ago I have noticed that they seem to suffer some from the co2. The Otos in particular act somewhat dizzy, slow, and inactive when co2 is on (they look better when it is off). Now, one would think I am overgassing, but DC is only ever light green and my Rasbora espei do not seem to react badly. I was wondering if Otos and shrimp are generally more co2 sensitive than others? I would love to hear your experience with this. I don't like the idea that a great tank should come at the expense of fish and shrimp well-being.

Thomas


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## bridgey_c (1 Oct 2013)

Hi Thomas,

I am no expert but I only have Otos, cherry shrimp and rasbora's in my 60l and I am 99.9% sure that cherry shrimp are the most sensitive to co2.

The only plant I consistently struggle with is hairgrass. I am fine with HC etc but for some reason my hairgrass never flourishes and always develops filamentous algae. For this reason I am always trying to increase my CO2 levels. I have breeding adult oto's and dozens of baby oto's and I have never seen them show any major symptoms of co2 problems. Every time I slightly increase the co2 levels however, even by half an hour, I kill a shrimp or two.I am always playing with different levels of surface movement and injection rates trying to improve things and I am always gutted when I see a shrimp struggling so I back off the co2 right away. I have never seen the rasboras show any signs of co2 toxicity.

I am probably right on the limits for my shrimp with regards to co2. my water has a DKh of 11 and I am around 6.8 ph at lights on, which is around the 45ppm mark. I have seen Tom Barr have his co2 levels a lot higher and his shrimp and fish are fine but I cant seem to replicate those levels. I have no idea why I struggle with hairgrass, I haven't solved that problem yet.......

If your plants are healthy then you can always decrease the co2 levels slightly and see what happens, you can always increase them again. I think surface movement has a big part to play in the welfare of the critters, maybe have a play with that.


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## TOO (1 Oct 2013)

Thanks for input, Bridgey.

Yes, considering your other thread your Otos don't seem to be doing too badly. Impressive, Oto breeding is quite rare as I understand.

The surface issue is one thing to play with. Since changing from metal jet pipes to lily pipes I have much less surface agitation (but also I think much better distribution and, from a plant perspective, it is a good thing to keep co2 in the tank rather than degassing).

Another theory might be Flourish Excel, which I add 2-3 times the recommended dosage. I will try and hold back on that for a few days.

Thomas


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## ceg4048 (1 Oct 2013)

bridgey_c said:


> I am probably right on the limits for my shrimp with regards to co2. my water has a DKh of 11 and I am around 6.8 ph at lights on, which is around the 45ppm mark


This is another optical illusion of The Matrix. There is no way you can determine the CO2 level in a tank from KH and pH. The CO2 level is much lower than you think. And that is why your hairgrass suffers.

Cheers,


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## bridgey_c (1 Oct 2013)

Hi ceg,

Is that because I cant accurately measure those values or is it something else? For instance, if I could magically get exact figures for Kh and Ph could I still get a false reading for co2?


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## Yo-han (1 Oct 2013)

Yes it would still be false because KH is not the only buffer in your aquarium. Phosphate is as well for example. Acids leaching from the wood lower pH without adding CO2 etc.


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## ceg4048 (1 Oct 2013)

That's right. Your tank produces lots of acids that drive the pH lower and which has nothing to do with the Carbonic acid from CO2. It doesn't matter therefore how accurate your pH and KH measurements are. The measurements are corrupted by the tank acids such as Nitric, Phosphoric and a series of Organic acids. That's why we put distilled water adjusted to a known alkalinity in the dropchecker, to isolate the sample  water from the tank water, and to be certain that any pH changes in the sample water is due only to changes in carbonic acid.

Unfortunately, the penalty paid is that the DC is hours behind and cannot determine instantaneous values. That's why it's better to take many direct pH readings over the course of the photoperiod to get a better idea of how the gas is behaving.

To answer the OP's question, shrimp are definitely more sensitive to CO2 toxicity, however, due to the slow response time of the DC it cannot always be ascertained what the CO2 concentration levels are at any location in the tank. If flow/distribution are suspect, the this makes it even more difficult to ascertain.

Cheers,


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## roadmaster (2 Oct 2013)

Were it me(and it ain't).. I would be more suspect of Excel at two to three times recommended dose and or low O2 values.
If fishes exhibited sluggish behaivor,directly after adding  3X the doseage recommended of Excel,the  I wouldn't overdose it again.
I'm with Clive on observing tank over course of photoperiod to determine what may or may not constitute too much gas for current resident's.
Could be reducing the once surface disturbance is maybe reducing O2 exchange of an evening when plant mass is using O2?
Oto's I have kept/am keeping,like cool ,oxygen rich water with moderate to more current.


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## TOO (2 Oct 2013)

roadmaster said:


> Were it me(and it ain't).. I would be more suspect of Excel at two to three times recommended dose and or low O2 values.


 
Thanks for this. I am beginning to think that it is in fact the Excel that is the problem, not the gas. Yesterday, I held back on the Excel and noticed more active behavior in the Otos. Too early to say if this is a pattern, but I think it likely is. Also, there is no reason to add the Excel from a co2 perspective as there is already sufficient gas. I have only been adding it in the upstart phase to avoid algae. Hopefully I won't get into trouble.

Thomas


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## dw1305 (2 Oct 2013)

Hi all,


roadmaster said:


> and or low O2 values.


 It could be the Excel, they are quite sensitive fish, or "Roadmaster's" suggestion. I think _Otocinclus_ probably do have a reasonably high oxygen requirement, Loricariids vary from extremely sensitive to low oxygen levels _(Pseudolithoxus, Hypancistrus_), to tolerant of extremely low oxygen levels (some _Hypostomus_ etc), depending on how rheophilic they are, and whether they still have the ancestral capacity (from their common ancestor with _Corydoras_ etc) to absorb atmospheric oxygen through the gut wall. I think _Otocinclus_ come from flowing water and don't gulp air, so that would suggest that they don't have much tolerance to very low oxygen levels.

Being small is an advantage in terms of having a high gill area to volume ratio, and if you have a look at these links in explains this and how CO2 and O2 diffuse in and out of the blood along their diffusion gradients  <Discus in a high tech planted tank | UK Aquatic Plant Society> & < Fish Respiration>.

Any-one who wants a more complete over-view, there is great "Powerpoint" that can be down-loaded from <http://www.hccfl.edu/br/> called "Fish Biology Respiration".

cheers Darrel


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## TOO (2 Oct 2013)

Thanks a lot for this Darrel. Very useful reads there, all bookmarked. Right now I am testing the Excel hypothesis, but I think it likely works in combination with the oxygen problematic. Especially since the only parameter changed was the move from metal jet pipes to lily pipes, which has altered the character of flow, and hence oxygenation, in the tank (see above).

Thomas


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## sparkyweasel (3 Oct 2013)

Otocinclus can breathe air (but may still be sensitive to high CO2 levels).

http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Air.pdf


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## flygja (3 Oct 2013)

I have dosed 4x recommended Excel values and haven't gotten any untoward oto deaths. Don't recall them looking uncomfortable either.


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## dw1305 (3 Oct 2013)

Hi all, 





sparkyweasel said:


> Otocinclus can breathe air (but may still be sensitive to high CO2 levels). <http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Air.pdf>


That is a useful post and link. Apparently _Otocinclus_ have a different air breathing apparatus morphology from all the other Loricariids, and Jonathan Armbruster has observed them air gulping in hypoxic conditions.

I've never noticed mine do it, although I suppose if they did it would be most likely to occur outside of the photo-period.

cheers Darrel


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## roadmaster (3 Oct 2013)

I run hydro sponge filter's on timer's at night, for tank's holding these fishes(oto's,pleco's,corydoras,loaches) after finding them all glued to water line at first light in my low tech tank's.This is where surface distrubance from spray bar's  just under the water line is strongest.
Used to use aquaclear 804's (old model#) with quick filter attachment,but flow was too much for the plant's to stay put,so I utilized the sponge filter's instead.I tucked them back behind the plant's and they are hard to see .
Low O2 condition's may not have anything to do with OP's problem but then again,,


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## dw1305 (3 Oct 2013)

Hi all,


roadmaster said:


> I run hydro sponge filter's on timer's at night, for tank's holding these fishes(oto's,pleco's,corydoras,loaches) after finding them all glued to water line at first light in my low tech tank's


 That is the one, rheophilic fish "_glued to the water line_" is the classic sign of low oxygen levels.

You get posts all the time on some of the catfish forums with this symptom, and people are always going "_It isn't low oxygen, because I have a bubble wall",_ or_ "my oxygen test kits says my oxygen is OK" etc_". When their fish subsequently asphyxiate it is always something else that killed them, and often, if they have any plants, they get the blame.

I eventually got fed up with these posts and rather than keeping on repeating the same replies I wanted to put all the "bits" in one place, which was why I wrote "Aeration and dissolved oxygen in the aquarium" <http://plecoplanet.com/?page_id=829>. Unfortunately it hasn't made much difference to the number of sadly asphyxiated "L numbers".

cheers Darrel


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## TOO (3 Oct 2013)

Thanks for all the insights!

The Excel hypothesis seems to hold: fish are more active now, but especially after co2 comes off. During the day when the tank is blasted with gas, they still seem a little uncomfortable, which means that the O2 hypothesis cannot be refuted. No gasping or gluing to the water line as described above, but quite inactive and not looking too happy (I know, how can I tell, and this is admittedly just a hunch since there are no clear symptoms other than inaction). But I also think these, as other Loricariids, are mainly nocturnal, so the fact that they are not active during the day may have something to do with their "lifestyle".

Thomas


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## dw1305 (5 Oct 2013)

Hi all,


TOO said:


> But I also think these, as other Loricariids, are mainly nocturnal, so the fact that they are not active during the day may have something to do with their "lifestyle"


 I think if Otos are happy and well fed they tend to spend most of the day resting. Mine always have some vegetables in the tank, and I very rarely see them until the evening. I think if your Otos are constantly active during the day they aren't getting enough to eat. Even though they are small fish they are potentially quite long lived, I've had my oldest ones at least 4 years.

cheers Darrel


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