# Surface agitation in co2 planted tanks.



## Puntius (31 Aug 2017)

Good day. 

As I read previously Surface agitation is needed for little o2 gasious exchange. While running co2 in your tank. There should only be a slight ripple effect on the surface... Without really breaking the surface... Thoughts on this people. 

Please advise. 

Thanks 

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## Zeus. (31 Aug 2017)

Both well worth a watch, Dennis Chong is Fantastic in his explanations IMO


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## dw1305 (31 Aug 2017)

Hi all,





Zeus. said:


> Both well worth a watch,


I'm not a CO2 user, but I think they made a lot of sense and they definitely were well worth a watch. 





Puntius said:


> As I read previously Surface agitation is needed for little o2 gasious exchange. While running co2 in your tank. There should only be a slight ripple effect on the surface... Without really breaking the surface...


As it says in the second video, it is more to do with the rate that CO2 is out-gassed at, and a large gas exchange surface (how-ever you achieve it) will make regulating CO2 levels easier.  When the plants are actively photosynthesising the water will be ~ 100% saturated with dissolved oxygen, so you can't really get any-more oxygen in the water.   

The other thing you have to take into account is the <"Root effect">, some fish (often rheophilic ones) don't have any physiological adaptations to high CO2 levels, and can be asphyxiated even when dissolved oxygen levels are high. The problem is that the haemoglobin in the blood transports both oxygen and CO2. If you have high CO2 levels in the tank water the gradient between blood CO2 and the water is reduced and CO2 diffuses out of the gill surface more slowly. If a CO2 molecule is bound to the haemoglobin molecule, it can't accept an oxygen molecule. (from <"Does surface....">).

cheers Darrel


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## Parablennius (31 Aug 2017)

Well, reminds me of when I was keeping mixed native freshwater fish. All was well except for the native bullheads, Cottus gobio, which were clearly asphyxiated despite the Loaches, Barbatula barbatula, or whatever it's called these days being fine. Had Ruffe, Gymnocephalus cernua and Gudgeon, Gobio gobio and they were all fine.


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## Tim Harrison (31 Aug 2017)

Excellent videos, the last is particularly relevant demonstrating the relationship between gaseous exchange and stable CO2; the correct balance of which is essential for decent plant growth, algae prevention, and the welfare of tank critters.


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## dw1305 (1 Sep 2017)

Hi all,





Parablennius said:


> Well, reminds me of when I was keeping mixed native freshwater fish. All was well except for the native bullheads, Cottus gobio, which were clearly asphyxiated despite the Loaches, Barbatula barbatula, or whatever it's called these days being fine. Had Ruffe, Gymnocephalus cernua and Gudgeon, Gobio gobio and they were all fine.


I was out this morning doing some invertebrate surveying (kick sampling in the By Brook, near Castle Combe) and we caught quite a few Bullheads (_Cottus gobio_), first ones I've seen for several years. They are now listed under <"Annex II"> of the EC Directive on the conservation of natural habitats and flora and fauna.

That would be a really difficult fish to keep without a chiller, as you say it would be the perfect example of a fish with a high requirement for dissolved oxygen, highly rheophilic and mainly found in shaded streams (usually with a gravel bed and woody debris present).  I assume they  eat _Gammarus (_freshwater shrimps_) etc. 
_
cheers Darrel


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## Tim Harrison (1 Sep 2017)

They were really common in the streams where I grew up in South Nottinghamshire, it's a great shame the species appears to be in decline, especially as our population is of European significance.
And I've just read that they are the only freshwater cottid found in the UK. The Cottidae (sculpins) are mostly marine fish, with around 300 species worldwide. Which I guess is one of the reasons why the population is so significant.


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## Paul195 (4 Jan 2018)

Fantastic videos from Dennis, learnt a lot!


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