Help: Where is the CO2 from my DIY?
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Old 03-09-2013, 03:08 AM   #1
Markharrislondoncanada
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Help: Where is the CO2 from my DIY?


Hi Everyone,

Can anyone help a novice to understand why he can't seem to get ~any~ pH drop in response to CO2 injection?

Hardware
-----------
I have a 35 gallon tank with 50 watts of light. I have a bio-wheel type HOB filter. I'm growing beginner plants, most of which seem to be doing well in this limited lighting - Vals, Amazon Swords, Crypt Wendii, Wisteria, "Mat Grass". I can't remember the gravel, but don't think it's anything special. I did recently add some very well rinsed laterite as a top up to the substrate. There is one piece of driftwood and a few non-carbonate rocks.

I'm currently running DIY CO2 into a Hagen ladder. I started with two 2 litre pop bottles, but have since added two more 1 litre bottles. All of them "T" into the Hagen ladder. I get from between 0.5 to 3 bubbles per second, depending on how long the bottles have sat. (I actually added the 3rd and 4th bottles to try to push enough gas pressure for a wood air stone, which I was able to do).

I know that the ladder isn't as efficient as a diffuser or an inline reactor. However, the bubbles enter the ladder at about 5mm in diameter and exit at about 1 mm. This tells me that most of the gas is dissolving (right?). I've tried placing the ladder in different parts of the tank - beside the filter and as far a way as possible from it.

I also tried bubbling the gas through the wooden airstone for a few days. The bubbles were relatively fine, and I let them climb up the ladder. I removed the airstone when no pH change was happening.

I have 10 cardinals, 4 platys and an OttoCat.

Water Chem
--------------
pH - 7.6
hardness - 80-100 mg/L
kH alkalinity - 100 mg/L (kH about 6 degrees)
temp - 78F
25-40% water change per week.
(all test kits are API and brand new).

I dose nutrients on a low-tech "as needed" basis. I test and try to target nitrate = 10-20 mg/L, Phosphorus = 0.5 mg/L, Iron=0.25 mg/L. Flourish micro added 1-2 times per week.


HELP
-----
Shouldn't I at least be seeing some pH drop due to the gas injection? I know that the Hagen ladder isn't that efficient, but from what I've read it isn't THAT bad either. I should be seeing something right? The pH-KH chart tells me that I hardly have any CO2 at all.

I should mention that this was a long established, but very undermaintained tank for several years. I just did a major gravel clean up in January, with two 80% water changes. The fish survived. There were only a few living Vals and mat grass at the time. I added the Amazon Swords and Crypts in early February. I actually did have lower pH for several days shortly after this rebuild (dropped to about pH=7, though on an older pH kit), and actually had pearling (streaming of bubbles from the newly planted Amazons and even some of the Vals), but this has since stopped.

The plants are doing well, with two Amazon swords having grown to the canopy. Algae is under control. So I guess this is "success". But I would like the CO2 to work, so I can someday try some more challenging plants.

Any ideas?

Thanks,

Mark
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Old 03-09-2013, 03:52 AM   #2
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Quote:
Originally Posted by Markharrislondoncanada View Post
Shouldn't I at least be seeing some pH drop due to the gas injection? I know that the Hagen ladder isn't that efficient, but from what I've read it isn't THAT bad either. I should be seeing something right?
Yes, you should be, given that you are injecting quite a bit of CO2.

However, I think the biggest concern is that your HOB filter (which is also a biowheel type HOB filter) will be creating excessive surface agitation such that any injected CO2 will diffuse quickly out of the water column.

Unless you are intend to buy a new filter, your solutions are somewhat limited.

You can try to raise the water level so that less surface agitation occurs. Removing the biowheel can help as well, but can be detrimental, for obvious reasons.

Quote:
Originally Posted by Markharrislondoncanada View Post
The pH-KH chart tells me that I hardly have any CO2 at all.
This is not the best way to determine how much CO2 you have in the water column, as this relationship relies on the assumption that two of the three factors are stable (in this case, you are assuming pH and kH are fixed, and that the only species contributing to carbonate hardness is bicarbonate; this is not the case in an aquarium). As such, this relationship cannot be relied upon in this manner.

Instead, using a drop checker with a 4 dkH reference solution is the better way to estimate the amount of CO2 you have. With a 4 dkH reference solution, the only species contributing to carbonate hardness will be the bicarbonate anion, and thus, the pH/kH/CO2 relationship can be used.
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Old 03-09-2013, 04:04 PM   #3
Markharrislondoncanada
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Thanks Darkblade,

Though I assume that it's not recommended, would I be able to test the influence of the HOB filter by shutting it off overnight? If surface agitation is a main culprit, and if I shut the filter off, would pH be expected to drop after just one 12 hour "night" period?

I will look into finding a drop checker. But is the ph-KH relationship (through pH and KH test kits) completely unreliable? Shouldn't I still see some kind of pH change, but just not be able to rely on the test kits for an "accurate" calculation of CO2?

In other words, if I eliminate the HOB, I should see better gas dissolution/distribution. And if I get a drop checker, I should be able to more accurate estimate the concentration.

Thanks,

Mark
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Old 03-09-2013, 04:20 PM   #4
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Try the drop checker. I run 2 HOB filters on my 38-gal and I'm not having any trouble keeping the drop checker in the green zone with DIY CO2. I only need two 2-liter bottles for the CO2, but I do have a glass cover on the tank.
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Old 03-09-2013, 08:08 PM   #5
Markharrislondoncanada
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Does anyone know where I can buy a drop checker and solution? I live in southern Ontario (London). Online only?

Thanks!
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Old 03-09-2013, 10:51 PM   #6
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Quote:
Originally Posted by Markharrislondoncanada View Post
Does anyone know where I can buy a drop checker and solution? I live in southern Ontario (London). Online only?

Thanks!
I could have provided you with some a few years ago (when I was in London doing graduate school )

Online is probably your best bet now. I know of a few sources in Toronto, but I doubt you want to drive/take the bus over.
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Old 03-10-2013, 01:27 AM   #7
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1) Try adding blackwater.
2) Distilled water
3) If you're that desperate how about plastic wrapping your tank top and then placing a glass lid.
4) Check you connections for leaks
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Old 03-10-2013, 06:59 AM   #8
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Quote:
Originally Posted by Markharrislondoncanada View Post
Thanks Darkblade,

Though I assume that it's not recommended, would I be able to test the influence of the HOB filter by shutting it off overnight? If surface agitation is a main culprit, and if I shut the filter off, would pH be expected to drop after just one 12 hour "night" period?

I will look into finding a drop checker. But is the ph-KH relationship (through pH and KH test kits) completely unreliable? Shouldn't I still see some kind of pH change, but just not be able to rely on the test kits for an "accurate" calculation of CO2?

In other words, if I eliminate the HOB, I should see better gas dissolution/distribution. And if I get a drop checker, I should be able to more accurate estimate the concentration.

Thanks,

Mark
What is the experation date on your Ph solution... maybe its out of date. Also instead of removing your HoB why not just remove the wheel part,keep it in a bucket of water so the bacteria doesn't die. I think it would be to harmful to keep the filter off overnight since the bacteria need oxygen to live too.

I use to have the ladder difuser in my 37 gallon and I had noticable co2 levels something is wrong. (seeing ph drop) and I also had a KH of around 10.

Also, do you see any pearling/ O2 being released by the plants that is also another sign that Co2 is actually in the water column.

ps, you can get a drop checker for 3-10 dollars shipped from evilbay. They also have packages available that come with 4dkh solution, there is also a seller that is selling them here on plantedtank but is a US seller.
http://www.plantedtank.net/forums/sh...d.php?t=267882

Last edited by latchdan; 03-10-2013 at 07:04 AM.. Reason: addition
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Old 03-25-2013, 05:19 PM   #9
Markharrislondoncanada
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For reference:

I made sure that my water level was as high as possible. I have a glass cover on 80% of the tank. I dropped the HOB pump to its lowest setting. I continue to have about 1-2 bubbles per second into my Hagen ladder. The bubbles usually decrease in diameter from about 4 to 1 mm. I have a brand new pH test kit and KH kit.

I was eventually able to see the pH drop from about 7.6 to 7.0. The pH drop did not occur until several days after I did a 40% water change. And even though I continued to add lots of gas, the pH rose back up again after about a week.

I did another large (40%) change about 2 weeks later. Once again, after a few days, the pH dropped from 7.6 to about 7.0.

My layperson's interpretation is that there is something in the tank (gravel?) that is buffering against a pH change. The influx of a good portion of new tap water temporarily removes some of the buffering capacity (KH and GH are about 100 ppm after the water change). This is why the gas is able to lower the pH significantly a day or two after the water change. But once the water has been in the tank for some time, the addition of CO2 doesn't produce a pH change.

I could be entirely wrong! But at the end of the day, the plants are growing well, and I am getting constant streams of little gas bubbles off some of the amazon swords.
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Old 04-02-2013, 03:24 PM   #10
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Default Further confirmation

The same phenomenon happened again. I did a 40% water change. CO2 was injecting at 2 bubbles per second, with the bubbles decreasing in diameter from about 4 mm to 1 mm at the top of the Hagen Ladder.

Within a few days, pH dropped from 7.8 to 6.8. Measurements in the morning, prior to lighting. KH and GH both around 100 ppm. The plants appeared to respond by producing lots of oxygen bubbles, including constant streams of microbubles from the Amazon Swords.

About a week later, even though the CO2 bubbles were still behaving the same way, I could not get the pH to drop below 7.4.

So, again, it looks to me like there is something in the tank (likely the gravel?) that progressively reduces the ability of the water to change pH overnight due to CO2. This appears to be only temporarily overcome by the addition of a large volume of new water to the tank.
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Old 04-02-2013, 03:51 PM   #11
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It is winter, and you live in Canada. When your house stays closed up for long periods, CO2 levels in your house can build up and affect the pH of your tanks. Next semi-warm day, try opening some windows for a little while.
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