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Discussion Starter · #1 ·
I have a 46g with three 2 liter DIY CO2 bottles. I try to average rotating one fresh bottle in each week. Usually it's a bit less often than that, but recently I've been a bit more aggressive, and yesterday's fresh bottle was probably the 3rd in just over two weeks, so maybe 5 to 6 days between fresh bottles.

Today I noticed a bit of pearling, something I hadn't seen except when adding fresh water (very high CO2 content in my well water). I don't usually bother calculating CO2 levels, but thought I'd have a check. My KH measured 8.4 and my pH 6.5. I think that means 80ppm CO2. Yikes!

The fish seem fine. I've turned on the air bubbler bar for the night. I'll see how things look in the morning. I think I should be targeting a pH of 7.0, but given the inconsistency of DIY CO2, that should be a low pH target that I only see the day after putting in a fresh bottle. Maybe I need to invest in a drop checker. Anyone have a recommendation (will probably be doing a Big Al's order soon).
 

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A drop checker with a reference 4 dkH solution would be your best bet. Trying to determine the amount of CO2 from just the pH and kH is not accurate, as the relationship between pH, CO2 and kH rely on the assumption carbonate buffers are the only thing contributing to kH, which is not the case in an aquarium.

Also, when you change your water, the pearling you see is not due to excessive CO2 content in the water, but excessive oxygen content.
 

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Discussion Starter · #4 ·
Also, when you change your water, the pearling you see is not due to excessive CO2 content in the water, but excessive oxygen content.
Really? I know the bubbles are O2 bubbles, but I thought they were the result of increased CO2, allowing more photosynthesis to happen, which increases plant O2 production.
 

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Really? I know the bubbles are O2 bubbles, but I thought they were the result of increased CO2, allowing more photosynthesis to happen, which increases plant O2 production.
Pearling and the "pearling" that you see after a water change are not the same. The "pearling" that you see after a water change is due to excessive oxygen content in the water.

Real pearling is when the oxygen being produced by the plants during photosynthesis becomes visible.
 

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Discussion Starter · #6 ·
Pearling and the "pearling" that you see after a water change are not the same. The "pearling" that you see after a water change is due to excessive oxygen content in the water.

Real pearling is when the oxygen being produced by the plants during photosynthesis becomes visible.
The pearling I see after a water change is a stream of small bubbles coming out of the plant leaves. Looks just the same as what I'm seeing now with my DIY CO2 in high gear. Why would the CO2 in my well water not induce photosynthesis pearling?
 

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Discussion Starter · #8 ·
Ok, I see your point. Pearling requires not only O2 production by the plant, but O2 saturation levels high enough to prevent the produced O2 from being dissolved into the water. However, I think it's a bit overstated to say it's just the O2 in my well water causing the pearling, and that CO2 in my well water plays no part.

In a planted tank with enough light and CO2, you see pearling without any introduction of O2 rich water. This is because the O2 produced by the plants has saturated the water enough O2 for pearling to happen. It seems reasonable to assume that introducing CO2 rich water could also cause enough increase in plant O2 production to raise O2 levels. Maybe this alone is enough to cause pearling, or as you stated maybe the O2 already in the new water is enough. Maybe you need a combination of both. I think all 3 are possible. If you want to know which is really happening in your tank, I would check carefully to see if pearling starts the instant you add the new water. If it does, then probably it it just the high O2 saturation in the new water. If there is some delay, the probably in increased CO2 is also playing a role. I'll watch my tank closer after my next water change to see when pearling starts.
 

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Some cities inject CO2 with water to keep the ph down so your pipes don't scale.

If you never see pearling, you need more CO2. I had a yeast can for a while and it would make plants pearl when it was working well. I don't think a 3 week old bottle does a lot of good? You might need to buffer your water a bit but you want pearling.
 

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Discussion Starter · #10 ·
Some cities inject CO2 with water to keep the ph down so your pipes don't scale.

If you never see pearling, you need more CO2. I had a yeast can for a while and it would make plants pearl when it was working well. I don't think a 3 week old bottle does a lot of good?
Depends on how quickly your bottles burn out. Mine start off at around 1 bubble per second. I just went to rotate one out today that was nearly 3 weeks old, and it was still producing at 1 bubble per 5 seconds. I imagine it was doing a bit better at two weeks, which is when it would have been swapped out if I only had two bottles in the rotation. I'm actually thinking maybe I should go with a 4th bottle.

Multiple bottles not only help you get the most out of each bottle, they also help keep CO2 production more consistent.

You might need to buffer your water a bit but you want pearling.
Please explain. I'm not sure what you mean by "buffer".
 

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got a quick que... I've never used DIY CO2, but planning on it for my new nano. why does some uses baking soda w/ their mix??? thnx.:biggrin:
 

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ah huh.... that explains using baking soda to make 4dKH water for the CO2 drop checker! thnx ya'll... :biggrin:
 

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baking soda is used all the time in pools and hot tubs to help adjust ph.
in diy co2 i beleive it keeps the water from becoming to acidic. acidic water kills yeast.
While this is true, the death of the yeast is not due to acidic conditions, but normally due to the accumulation of ethanol in the mixture.

This is why I don't add baking soda to my DIY mixtures; it is just another thing to remember to add, and I want to keep DIY as simple as possible.

ah huh.... that explains using baking soda to make 4dKH water for the CO2 drop checker! thnx ya'll... :biggrin:
I am not sure how jreich's answer explains why baking soda is used for making the 4 dkH reference solution. It is used only because it is a common reagent that can be bought cheaply, etc. You could theoretically use any source of carbonate, as long as it was relatively pure (i.e. I could easily use sodium carbonate, potassium carbonate, etc., as long as I recalculated all the measurements).
 

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While this is true, the death of the yeast is not due to acidic conditions, but normally due to the accumulation of ethanol in the mixture.

This is why I don't add baking soda to my DIY mixtures; it is just another thing to remember to add, and I want to keep DIY as simple as possible.


I am not sure how jreich's answer explains why baking soda is used for making the 4 dkH reference solution. It is used only because it is a common reagent that can be bought cheaply, etc. You could theoretically use any source of carbonate, as long as it was relatively pure (i.e. I could easily use sodium carbonate, potassium carbonate, etc., as long as I recalculated all the measurements).
sorry mixed up KH w/ PH... :eek5: ddnt sleep all night :D
 

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Discussion Starter · #17 ·
My water starts at a pH of about 8.2 and dKh of about 9. I get good production for much longer now that I add about 3 tablespoons of baking soda. Mine used to start dropping off to a bubble every 10 seconds after about a week. Now I still get a bubble every 5 seconds after about 3 weeks.

I decided to start adding baking soda after I experimented with a "spent" bottle, and found that I got a lot more production out of it just by adding a bunch of baking soda too it.
 
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