CO2 - Which is right and other questions - The Planted Tank Forum
 
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post #1 of 4 (permalink) Old 01-13-2014, 07:05 PM Thread Starter
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CO2 - Which is right and other questions

I've read a bit on the CO2 topic here and elsewhere and have just a few questions for clarification. This area seems like a very tricky balancing act and as this is my first time using a CO2 diffuser in a tank, I need to get this straight.

My set up:

6.6 gallons
Up-Aqua CO2 system
Baseline Ph: 7.6
Baseline kh: 30 ppm

1. In one thread, a person said 3 ppm of CO2 was the right amount. Other articles and threads say 15-35 ppm of CO2 is right. Which is correct? Gotta get this one right.

2. The dumbest of the questions. ppm is independent of the amount of water, correct? 15ppm of CO2 in 75 gallon is the same as 15ppm of CO2 in my tank. The only differing bit is the amount of CO2 needed to achieve the desired CO2 amount.

3. I just set up the CO2 unit in my tank. I plan to run it for 24 hours before checking CO2 levels. I am running roughly 1 bubble every 6-7 seconds (manufacturer said 1 every 3 seconds but setting a precise release amount is very difficult) and the CO2 is entering the tank at a small trickle.

When I test the water tomorrow, do I test it right out of the tank or take out some water and let it sit a while before testing?

4. Will the CO2 ppm drop when I introduce live plants?

5. To adjust the ph, I use an acid and alkaline buffers when needed) made by Seachem. I am confused about whether or not it is ok to use them to set the needed ph/kh to achieve the desired CO2 ppm. In some stuff I have read, it makes it sound like the moment I introduce them into my water it will forever throw off any CO2 measurements.

6. A more technical (second dumbest question) question: The CO2 ppm values the calculator tools provide based on existing kh and ph values are based upon a constant flow rate of CO2...correct? Set me straight here if I am wrong.

If that's correct, does that also mean that if I want my ph set at a specific point, can I adjust the amount of CO2 flow into the water to achieve the desired ppm rather than adjusting the ph to get that same ppm? I ask because the calculators I have used are telling me that to get a CO2 ppm value of 15 based on my baseline parameters, I must set my ph at around 6.4 to 6.6, lower than I wish for a betta.

That should about do it for now.

Last edited by rpadgett37; 01-13-2014 at 07:18 PM. Reason: Clarfication of last question
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post #2 of 4 (permalink) Old 01-13-2014, 08:25 PM
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I have never tested to get a desired ppm. I think in your first question though, the person in the thread was referring to bps (bubbles per second). I think most people achieve the desired amount of CO2 with 2-3 bps.
pH will drop with the addition of CO2 and rise again later once CO2 turns off. This is very normal and doesn't affect the fish at all.
You can get a drop checker for your tank and watch the color change. Slowly raise the amount of gas and watch the drop checker change colors to know when you have a sufficient amount of gas. You can read a little more here.
I don't use either method. I setup my CO2 system and over the course of about a week, I slowly added more bps until fish started gasping. I then turned the gas back down just a little to when the fish are comfortable.
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post #3 of 4 (permalink) Old 01-13-2014, 10:48 PM Thread Starter
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Ah... I knew it was time to get my eyes checked again. I adjusted the flow to 1 bps.
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post #4 of 4 (permalink) Old 01-14-2014, 08:59 PM
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Quote:
1. In one thread, a person said 3 ppm of CO2 was the right amount. Other articles and threads say 15-35 ppm of CO2 is right. Which is correct? Gotta get this one right.
Cah925 already addressed this one... and he pretty much also told you the least headache way to manage all these things you're wondering about. I will stress that he mentions he adjusted it over the course of a week! You want to slowly add. Watch for a day and then add just a little more. And do it on a day when you're home. Otherwise, u might just come back to a tank of dead fish.

Anyway, for the sake of your curiousity, I'll try to address some of the other questions.

Quote:
2. The dumbest of the questions. ppm is independent of the amount of water, correct? 15ppm of CO2 in 75 gallon is the same as 15ppm of CO2 in my tank. The only differing bit is the amount of CO2 needed to achieve the desired CO2 amount.
Yes, you could say that. I understand parts per million as a fraction. So 15/1000000 in a 75g is the same "concentration" as 15/1000000 in your 6.6g
http://groups.molbiosci.northwestern...r_million.html

Quote:
3. I just set up the CO2 unit in my tank. I plan to run it for 24 hours before checking CO2 levels. I am running roughly 1 bubble every 6-7 seconds (manufacturer said 1 every 3 seconds but setting a precise release amount is very difficult) and the CO2 is entering the tank at a small trickle.

When I test the water tomorrow, do I test it right out of the tank or take out some water and let it sit a while before testing?
you can and probably want to do it both ways. right out the tank will give you the ph before degassing and if you let it sit long enough (another 24 hours) or shake it vigorously, you will degas it and it should in theory give you back the same ph as your regular water before the ph injection. This is how you can measure how much ppm co2 is in your tank based on the ph/kh/co2 chart. Co2 testing methods

Quote:
4. Will the CO2 ppm drop when I introduce live plants?
Hmm. It ought to if the plants are consuming it. This is why you have to figure out how much to add so that it doesn't drop so far that you are running into a level of deficiency.


Quote:
5. To adjust the ph, I use an acid and alkaline buffers when needed) made by Seachem. I am confused about whether or not it is ok to use them to set the needed ph/kh to achieve the desired CO2 ppm. In some stuff I have read, it makes it sound like the moment I introduce them into my water it will forever throw off any CO2 measurements.
It will throw off the co2 measurement in addition to some substrates that are known to soften water. Since you're trying to use the ph to run against the chart, you're getting a false sense of ph if it's more than just the co2 adjusting it. Anyway, as cah925 said, co2 will fluctuate your ph and it doesn't do it the same way as buffers do ( via Total Dissolved Solids ) so the fish will tolerate it okay. Most planted aquarists don't even concern themselves too much with ph levels. Usually, as long as you don't mess with the buffers, it'll keep a stable level of TDS and your fish will adapt to it fine. See this thread... especially post #11 https://www.plantedtank.net/forums/sh...ad.php?t=92766

Quote:
6. A more technical (second dumbest question) question: The CO2 ppm values the calculator tools provide based on existing kh and ph values are based upon a constant flow rate of CO2...correct? Set me straight here if I am wrong.
It's based on whats in your tank. Your flow rate only matters in what it puts into the tank. Think of water flowing out of your faucet into the sink. Imagine the co2 ppm is the amount of water in your sink and the drain is the plants consuming your co2 and degassing at the water surface. If you can't drain as fast as the water flow, your amount of water will increase. If your plants don't consume enough of your co2 or you don't degas enough, your co2 ppm will steadily increase. If you shut off the flow, the co2 ppm will decrease (just as your water drains out) .. so, I think you're either mixing in two independent things or I'm confused in interpreting what you wrote.

Quote:
If that's correct, does that also mean that if I want my ph set at a specific point, can I adjust the amount of CO2 flow into the water to achieve the desired ppm rather than adjusting the ph to get that same ppm? I ask because the calculators I have used are telling me that to get a CO2 ppm value of 15 based on my baseline parameters, I must set my ph at around 6.4 to 6.6, lower than I wish for a betta.
So this goes back to TDS ph fluctuations vs co2 ph fluctuations in your question 5. Considering that they're different, you may not get the effect that you want. By adjusting the ph with your buffers, you're essentially falsifying the co2 reading so your 15ppm will not be truly caused by 15ppm of co2. It would've been caused by some level of co2 + your buffers.

But this all goes back to worrying too much about the specifics and actually introducing new problems. Cah925 has already pointed to the method of least headache.

Don't use buffers to affect the TDS. This allows for better stability and then your fish will be ok from a ph standpoint in that aspect.
Co2 ph fluctuations don't matter to fish so it'll be okay from a ph standpoint in that other aspect.
What you REALLY need to worry more is about your fish suffocating from too much ppm of co2. We've all killed fish faster that way than with ph problems. So, I stress again, add co2 slowly and watch your fish to make sure it doesn't suffocate and then your fish will be ok.
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