# Need small fish that can handle high CO2



## oblongshrimp (Aug 8, 2006)

I am looking for some small fish that can handle higher levels of CO2. Suggestions would be appreciated. Thanks .


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## JanS (Apr 14, 2004)

If your levels are too high for some fish, I wouldn't risk putting any fish in the tank until you lower it some. Even if a few of them can survive it, it isn't the best for them.
What are the levels in your tank?

If it's in the safe zone, you can pick pretty much any fish that suits your fancy, as long as it's appropriate for a tank your size.


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## vancat (Nov 5, 2004)

Well said, jan.


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## Jimbo205 (Feb 2, 2006)

JanS., 

do you find BIO-Wheels help keeping CO2 within the safe zone for fish? 

Jim


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## JanS (Apr 14, 2004)

Hi Jim, 

I don't use bio-wheels, because I've heard they aren't the most effective form of filtration, but of course with no experience, I can't give a definite answer either.... 

With my high KH, and using a controller, I have never experienced any problems with any problems with the C02 going above the safe level, but I'm sure every case is different.


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## Round Head (Feb 28, 2006)

Just put an airstone in there and the fish will be all right.
The community in my tank does very well in high CO2 with an airstone.
I tried to remove the airstone on day for about 2 hours and they all at the surface gasping for air. Then put the airstone back in and all as well. And I don't belief the airstone is going to mess with your CO2 level, it just add extra O2 for the fish.


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## ryzilla (Feb 3, 2007)

Jimbo205 said:


> JanS.,
> 
> do you find BIO-Wheels help keeping CO2 within the safe zone for fish?
> 
> Jim


I used to use an emperor 280 on my 30g hightech when I first got into the hobby. I soon became aware that without pressurized CO2 I waas never going to get high enough CO2 levels because of the massive amounts of surface agitations that was releasing the CO2 from the water column. The biowheel is not the problem, it is the surface agitation created by power filters. Generally planted high-techers stay away from the power filter, but the low-techers it benefits by pulling CO2 from the atmosphere and shoving it into the aquarium. A powerfilter in a lowtech tank my raise the CO2 levels slightly higher than using a filter that does not agitate the water surface. I advise against the powerfilter in any application but a lowtech(non co2) application.


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## Jimbo205 (Feb 2, 2006)

I am sure that someday I will purchase and try a canister filter. And I know that many people swear by them. For myself, I have never heard anything convincing enough for me to make the switch. Maybe when I eventually get a large enough tank I will get one. 

I have heard so many positive things about BIO-Wheel and Hang On Back filters and really do like both of mine. For myself, in one of my tanks with DIY CO2; I make sure the CO2 bubbles float up underneath the current and get pushed around by it. 

I know some hobbyists use CO2 - diffusion DIY 'Catalysts' or engines or some such and like them very much. I like to watch the CO2 bubbles in the tank and listen to the wonderful sound of the water from the BIO-Wheel 'waterfall' and the thought that it keeps my fishies breathing at night time. 

I have my filter set on a timer where it turns on during the night time and shuts off when the light from the window (much brighter than man-made I am told) and also when my light fixture turns on - so I can again watch the bubbles rise - this time from the pearling of O2 from the HM. 

JanS. thank you very much for your answer. 

oblongshrimp, I would love to hear more about your tank, fish and co2.


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## epicfish (Sep 11, 2006)

Round Head said:


> Just put an airstone in there and the fish will be all right.
> The community in my tank does very well in high CO2 with an airstone.
> I tried to remove the airstone on day for about 2 hours and they all at the surface gasping for air. Then put the airstone back in and all as well. And I don't belief the airstone is going to mess with your CO2 level, it just add extra O2 for the fish.


Running an airstone causes surface agitation when the bubbles pop. This causes outgassing of your CO2.


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## eklikewhoa (Jul 24, 2006)

I don't understand why one would add an airstone or use a filter that would out gas your co2 when you could just lower it some...........maybe I am missing something here.


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## JanS (Apr 14, 2004)

eklikewhoa said:


> I don't understand why one would add an airstone or use a filter that would out gas your co2 when you could just lower it some...........maybe I am missing something here.


That's why I prefer to use a controller with my setups. It just shuts the C02 off when it's not needed, rather than running it 24/7 and having to do something to out gas it.  
Not that pressurized C02 is that expensive, but I still don't like to waste anything if I don't have to.

Jimbo, I really like the HOB's without the bio-wheels too. I just keep the water level up high enough that it's not creating surface agitation.


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## Round Head (Feb 28, 2006)

I am curious now.
You guys are saying that an airstone bubbling air on one side of the tank is going to gas out CO2 concentration that will affect the entire tank?
The way I see it, air from the stone is being distributed with the CO2 instead of capturing CO2 in the water to gas it out. Please explain this in more details.


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## Laith (Sep 4, 2004)

Round Head said:


> I am curious now.
> You guys are saying that an airstone bubbling air on one side of the tank is going to gas out CO2 concentration that will affect the entire tank?
> The way I see it, air from the stone is being distributed with the CO2 instead of capturing CO2 in the water to gas it out. Please explain this in more details.


It's not a question of "capturing CO2 in the water to gas it out". It's simply that an airstone causes more surface agitation. More surface agitation = more surface area and more surface area means more gaseous exchange. So more CO2 is lost to the air.


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## eklikewhoa (Jul 24, 2006)

JanS said:


> That's why I prefer to use a controller with my setups. It just shuts the C02 off when it's not needed, rather than running it 24/7 and having to do something to out gas it.
> Not that pressurized C02 is that expensive, but I still don't like to waste anything if I don't have to.
> 
> Jimbo, I really like the HOB's without the bio-wheels too. I just keep the water level up high enough that it's not creating surface agitation.


Well, technically it's a good amount of money wasted on the air pump and such as well as loosing the co2.


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## eklikewhoa (Jul 24, 2006)

Round Head said:


> I am curious now.
> You guys are saying that an airstone bubbling air on one side of the tank is going to gas out CO2 concentration that will affect the entire tank?
> The way I see it, air from the stone is being distributed with the CO2 instead of capturing CO2 in the water to gas it out. Please explain this in more details.


The bubbles coming out of the airstone is not what you think, it does nothing O2 wise. The surface agitation is where the O2 comes from and at the same time it out gasses the co2. Surface agitation helps out gas co2 which in terms leaves more o2 for the fish to use in normal circumstances but since we are introducing co2 into the tank for plants we wanna keep from doing so.


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## bristles (Mar 7, 2006)

Try some Amandae tetras (copper color) they are quite small, as for high Co2 levels most fish can tolerate a fair dose, that said just keep an eye on them and if you see them gasping at the surface dial down the gas.


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## apistaeasy (Jul 16, 2004)

Their is no reason to have your CO2 levels so high that fish cannot properly survive in your tank.
Fish can tolerate levels up to 60-70 ppm! (Any fish, some need to be acclimated to your parameters by a drip system) Above 30-40 ppm your plants cannot absorb CO2 any faster. You have 20-40 ppm too much CO2 if you cannot keep fish alive in your tank.


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## bigtroutz (Nov 17, 2006)

eklikewhoa said:


> The bubbles coming out of the airstone is not what you think, it does nothing O2 wise. The surface agitation is where the O2 comes from and at the same time it out gasses the co2. Surface agitation helps out gas co2 which in terms leaves more o2 for the fish to use in normal circumstances but since we are introducing co2 into the tank for plants we wanna keep from doing so.


erm. not exactly. Aerator bubbles themselves can significantly contribute both O2 and CO2 to the water column. All of these exchanges of gasses MUST be thought of as equilibria of concentrations where diffusion is the major empowering factor.

CO2 would diffuse from the aerator bubbles (as well as the surface) into the water column as the partial pressure of CO2 was lowered by plant uptake. Likewise, CO2 bubbles will diffuse into the water as the CO2 bubbles rise to the surface.

The concentration gradient is the major factor in the direction and speed of diffusion. Contributions of flow and mixing enhance the effect by continually providing new water with maximal concentration differences.

What we are doing by bubbling CO2 gas into water is creating a CO2 supersaturated solution. What we are doing by not disturbing the surface film of this supersaturated solution is minimizing the rate of the diffusion process.


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## Round Head (Feb 28, 2006)

bigtroutz said:


> erm. not exactly. Aerator bubbles themselves can significantly contribute both O2 and CO2 to the water column. All of these exchanges of gasses MUST be thought of as equilibria of concentrations where diffusion is the major empowering factor.
> 
> CO2 would diffuse from the aerator bubbles (as well as the surface) into the water column as the partial pressure of CO2 was lowered by plant uptake. Likewise, CO2 bubbles will diffuse into the water as the CO2 bubbles rise to the surface.
> 
> ...


You sound like a Chem E. Me too.


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## oblongshrimp (Aug 8, 2006)

Well I know my rainbow fish do not light the higher CO2 in my 120gal tank because later at night they are gasping at the surface even though my rummynose are swimming around happily at the bottom of the tank.


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