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Discussion Starter · #1 ·
This is my experience. I have a pH controller and I can accurately regulate the CO2 levels in my tank. I can say that in my aquarium, levels of CO2 above 15 ppm have negative effects on some of my aquarium fish.

15 ppm is dark green to blue green on a drop checker so this is lower than many people keep their tanks.

OK probably no one here knows the CO2 level of their tanks but what color do you think your drop checker should be at? I know that a number of people think that when their drop checker goes yellow their fish are at risk. I think that when your drop checker goes green, your fish are not happy.

Where is your drop checker?
 

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in my experience i go with how many CO2 bps i'm injecting into my tank, and with what my pH meter tells me. my plants grow nicely and my fish are healthy. i don't need a drop checker or pH controller to tell me this.

so i'm not going to worry about the doom and gloom that i'm getting from your post. but i'm sure some people will consider your "...CO2 is bad for fish!" suggestions.
 

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Hi Ray,

I use a drop checker with 4.0 kh/dh water and 4 drops of indicator solution. I shoot for blue green / dark green which should be 30 PPM. As the plants grow I have to increase the flow, conversely if I do a large trim or restart a tank have to remember to decrease the flow. My plants are growing well with minimal algae.
 

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I don't know about that. On my 26 gallon bowfront, it is a bit overcrowded and i know i have at least 25ppm of co2 and had upwards of i would say 40 or more.. Not until then did i remotely begin to see signs of stress. I think i have a problem of not enough oxygen than too much co2. There are 6 3+inch discus in there right now a a handful of other small fish and a lot of plants. I have really good circulation and have check the co2 in a few areas in the tank. I think it is really important to have good flow if you run your co2 high because some areas could become really much higher in concentration that you think, and i think that is where one can run into problems.

Tom Barr will tell you that 30ppm is quite safe for fish, and i know he has experimented with higher levels of co2. I have read that smaller fish are more tolerant of higher co2 levels. In the future depending apon your goals, we may see levels greater than 30ppm become the norm. I will say i think it is risky to get around 30ppm or higher without a ph controller.

Stevie D
 

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What type of negative effects are you noticing, did they stop breeding are they panicking? How many tanks have you observed this on? Is the 15ppm for tanks with low light or for high light tanks?
 

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I suspect it would be prudent for you to double check the calibration of your pH meter and the dKH of your drop checker's solution before you go off dismissing the work of numerous others on the subject.

Personally, I know my 4dKH solution is spot-on as I made it myself from baking soda whose moisture content was known and corrected for and water that is of the highest purity, right from the tap of a Milli-Q Gradient A10 TOC polishing unit fed by an Elix water system (top shelf stuff, even by lab standards). When my drop checker is green, I'm in the 15PPM-30PPM CO2 window. My fish are fine.

pH controllers are only as good as their probes. If probes are neglected, CO2 delivery accuracy will suffer. If your probe gets gunked up at a pH above your set point, your CO2 tank will remain "on" until the pH drops to a certain point - which may be never, as far as your probe is concerned. You should also regularly calibrate the probe using standard buffers bracketing the range of pH values you anticipate the probe seeing. In addition to accuracy, you need to pay attention to the response time of the probe.

pH controllers are not "set it and forget it" devices.
 

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my drop checker is at an "olive" colour. I am watching it carefully. My observations is when the bottle is low on co2, the drop checker goes blue green. I've been feeding my tank for months prior to the drop checker. The only time this is going to change is when I get my DIY and the distilled water I require. I don't want to be trying to spend hours distilling it in my kitchen again.
 

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Discussion Starter · #8 ·
Hi Ray,

I use a drop checker with 4.0 kh/dh water and 4 drops of indicator solution. I shoot for blue green / dark green which should be 30 PPM. As the plants grow I have to increase the flow, conversely if I do a large trim or restart a tank have to remember to decrease the flow. My plants are growing well with minimal algae.
My feeling is that you have the perfect tank but I doubt that your CO2 is at 30 ppm.

Dark green corresponds to a pH in your drop checker of about 7.0. The CO2 level that corresponds to this is about 12 ppm which agrees with my own observations.
 

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Discussion Starter · #9 ·
I don't know about that. On my 26 gallon bowfront, it is a bit overcrowded and i know i have at least 25ppm of co2 and had upwards of i would say 40 or more.. Not until then did i remotely begin to see signs of stress. I think i have a problem of not enough oxygen than too much co2. There are 6 3+inch discus in there right now a a handful of other small fish and a lot of plants. I have really good circulation and have check the co2 in a few areas in the tank. I think it is really important to have good flow if you run your co2 high because some areas could become really much higher in concentration that you think, and i think that is where one can run into problems.

Tom Barr will tell you that 30ppm is quite safe for fish, and i know he has experimented with higher levels of co2. I have read that smaller fish are more tolerant of higher co2 levels. In the future depending apon your goals, we may see levels greater than 30ppm become the norm. I will say i think it is risky to get around 30ppm or higher without a ph controller.

Stevie D
Here is the experiment you need to do. Start at no added CO2 and observe the activity and the mating behavior of your fish. Keep them at this level for a few weeks to confirm how they act. Then increase the CO2 to 5 ppm. and check them out for a week or two. Increase CO2 to 10 ppm and see how they react after a week or two. Continue increasing CO2 until you are sure you notice a change in their behavior. Then drop the CO2 back. If the fish return to their normal behavior you know that CO2 is causing a problem.

BTW You will notice a change in your fish behavior long before they are at the top of the tank sucking in air.
 

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Discussion Starter · #10 ·

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Discussion Starter · #11 ·
I suspect it would be prudent for you to double check the calibration of your pH meter and the dKH of your drop checker's solution before you go off dismissing the work of numerous others on the subject.

pH controllers are only as good as their probes. If probes are neglected, CO2 delivery accuracy will suffer. If your probe gets gunked up at a pH above your set point, your CO2 tank will remain "on" until the pH drops to a certain point - which may be never, as far as your probe is concerned. You should also regularly calibrate the probe using standard buffers bracketing the range of pH values you anticipate the probe seeing. In addition to accuracy, you need to pay attention to the response time of the probe.

pH controllers are not "set it and forget it" devices.
Good advice but I don't think you have actually used a pH controller.

I calibrate my controller about every other week. I have a pocket pH meter that I use to verify my controller every few days. I also have a drop checker that I use to verify that my controller is working.

I can measure the CO2 level in my tank to +/- 2ppm.
 

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Is this a reliable way to quantify the amount of CO2 in your tank? Measuring the pH change of a small amount of tank water that has sat out in a paper cup for 24 hours compared to that inside the tank. A difference of 1 degree is supposed to equal 30 ppm.
 

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Discussion Starter · #15 ·
This is a really good idea but there is a problem. In every tank there are different chemicals that affect the pH of the water. Each tank is unique; so, when you take CO2 out of the water (letting it sit) you cannot know what effect these chemicals have on the change in pH.

The way to overcome this is to add a known quantity of CO2 into your tank and find out how much the pH changes. I explained how to do this here:

http://www.aquaticplantcentral.com/forumapc/equipment/56522-how-calibrate-your-drop-checker.html
 

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I agree that normal behavior stops before they are gasping at the surface for air and this dose stress the fish, If that is what you are saying. Fish behavior should be a concern when adding co2 not just plant growth and algae control. But I know many who have had fish breed and thrive in water with 30 ppm co2 (ph meter proven). The drop checker is a lose science and men are more prone to color blindness than women. This is why I think of the drop checker as a base line needing fine tuning. Fish behavior being a key factor among others. I also know those who have tested water in nature and found 30ppm co2.
 

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I agree that normal behavior stops before they are gasping at the surface for air and this dose stress the fish, If that is what you are saying. Fish behavior should be a concern when adding co2 not just plant growth and algae control. But I know many who have had fish breed and thrive in water with 30 ppm co2 (ph meter proven). The drop checker is a lose science and men are more prone to color blindness than women. This is why I think of the drop checker as a base line needing fine tuning. Fish behavior being a key factor among others. I also know those who have tested water in nature and found 30ppm co2.
A pH meter won't prove that there's 30 ppm CO2 in the water. You need a CO2 dissolved gas analyzer. I have a pH meter and I wish I knew how much CO2 I had in my aquarium.
 

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From Ray-the-pilot:
The CO2 level that corresponds to this is about 12 ppm
Maybe I'm wrong, but isn't all this based on some presumed relationship between pH and CO2....and doesn't kH figure into this equation?

How does all this relate to this....http://www.aquaticplantcentral.com/forumapc/general-aquarium-plants-discussions/56902-co2-calculator.html

According to that, then depending on the amount of Phosphates in your tank, your equation may be unreliable?

Is it possible to get to the factual truth about this? Is there a chemist in the house?

In the words of the immortal John Lennon,
"Im sick and tired of hearing things
From uptight, short-sighted, narrow-minded hypocritics
All I want is the truth
Just gimme some truth"

 

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A pH meter won't prove that there's 30 ppm CO2 in the water. You need a CO2 dissolved gas analyzer. I have a pH meter and I wish I knew how much CO2 I had in my aquarium.
Tom barr did prove this with a co2 dissolved gas analyzer ( I don't recall saying any thing about a ph meter). He has also done a lot of studying with this analyzer on many different tanks. As for a chemist I believe ray is one.
 
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