Creating CO2 naturally (Ended With Failure - insert sad kitten) - The Planted Tank Forum
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post #1 of 82 (permalink) Old 06-20-2019, 04:22 PM Thread Starter
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Lightbulb Creating CO2 naturally (Ended With Failure - insert sad kitten)

So I have a lot of time to think about aquariums but not much space to build one until after my wife and I buy a new house. This has lead me down several experimental rabbit holes as a fun way to pass the time.

My latest thought is wondering if its possible to simulate the natural process of co2 generation in an aquarium. I previously did an experiment (which failed) where I tried to introduce elevated levels of co2 through dissolving regular air into an aquarium through a reactor. During the course of that experiment it was pointed out to me that co2 forms in streams and lakes etc through the decomposition of organic matter and through the dissolution of carbonic rocks. So can we do this in an aquarium?

My proposed experiment would involve a bucket that would be used as a reactor of sorts. In the bucket would be layer(s) of soil and carbonic rocks (limestone probably though obviously open to suggestions). Water would run through the bucket constantly. The soil would naturally decompose and the rocks being reactive would dissolve. Both processes would release carbon into an aquarium. If I also aerate the water I should get at least some bonding of carbon to oxygen.

Potential problems with this idea include but are likely not limited to:

1) Difficulty in generating enough co2 to be worth the effort
2) The limestone will raise ph and hardness
3) Potential for soil being spread throughout the aquarium instead of staying put in the reactor

If the experiment is successful then problem 1 is solved. For problem 2 it is my hope to balance the amount of soil to rock in the aquarium. Hopefully the soil can reduce the hardness and ph. It will definitely be a balancing act to have the right soil mix (peat moss added etc) to counter the ph and hardness while still allowing for the carbon to be released and bond to the oxygen. Problem 3 will be solved by making sure the flow of the water does not directly disturb the soil. Possibly using baskets to hold the soil and alternating that with baskets of rock? Or using the rock as a "cap" for the soil? Will need to play with the design of the rock and dirt reactor to figure out the best way.

In the end I am confident this could work somehow because it does work in the natural environment all the time. The issue to my mind is not if it can be made to work, but whether it can be made practical and work. If I need a dump truck of soil to generate 20 ppm of co2 in a 10 gallon aquarium then its not practical. If I can have a 5 gallon bucket of rock and soil to do the same, then its potentially something of interest.

To do the experiment I will need two 5 gallon buckets, a pump, an air pump, some plumbing parts, potting soil, and crushed limestone. I will also need some way to layer the limestone and soil. I would like a way that is easily removable such as baskets but I may settle for something simpler.

One 5 gallon bucket would act as my "aquarium" while the other would be my reactor. I would pump water from one to the other and back out again in a loop. I would also aerate the water along the way. After running it for a while I would test the water for co2.

Thoughts? Suggestions? I am very open to ideas on how to run this experiment. The creating and running of the experiment is fun for me so know in advance I don't think this is a waste of time even if it fails. If it works it would be pretty fantastic and the cost of running the experiment will be limited to buying some crushed limestone and maybe some plumbing parts as I have the other materials already.

Last edited by minorhero; 09-08-2019 at 12:28 AM. Reason: results
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post #2 of 82 (permalink) Old 06-20-2019, 05:36 PM
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I love that you're willing to experiment and applaud your efforts! I am skeptical of your design idea though. My initial thought is it might be impossible to duplicate nature this way in an enclosed system. The issue of raising of the pH and hardness is real, and from my limited experience with acid buffering soils, I think the limestone is going to exhaust them. So at best, every 6 months or year (how long it takes would probably be determined by amount of KH going in) the entire substrate would need to be replaced. And besides these ADA type substrates being pricey, that's not something we're going to want to do to our planted tanks. My second thought is the decomposing soil and the organics it would (surely) produce. Even if you can keep particulates out of the aquarium water, dissolved solids would be another matter. It's worth setting up and testing just for the potential knowledge gained though. It seems almost like a Bizzaro world calcium reactor. In spite of my skepticism of this working, I hope you do it and manage to work out all the kinks. The hobby needs something between DIY and pressurized systems. I promise if you make it work, we'll all call it the Minor Hero Method!

Nothing good happens fast in an ecosystem.
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post #3 of 82 (permalink) Old 06-20-2019, 05:50 PM Thread Starter
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Thank you for the kind word Blue Ridge Reef!

Definitely the soil in the reactor should be exhausted eventually. That is one reason why I want a system where its easy to replace. In my mind I imagine this reactor to be kind of like a canister filter with stacked baskets of material. So many baskets of soil to so many of limestone etc. Then as the soil becomes exhausted you pull them out, replace with new soil and put them back in. Thats a bit far down the road. First I just need to see if it even works at all heh.
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post #4 of 82 (permalink) Old 06-20-2019, 07:48 PM
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Oh, I misread and assumed that Aqua Soil was going in the display, not just in the reactor. That would certainly make it easier to replace than uprooting all the plants and starting the tank over. I do doubt that it packs nearly as much punch in the other direction as limestone, and the ratio would probably be very high in favor of soil to lime. Interested to see what you come up with.

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post #5 of 82 (permalink) Old 06-20-2019, 07:58 PM
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I have been wondering the same thing. I have notice in co2 additive fluvic acid and humic acid are used. I have wondered if adding those products in the soil would create Co2.
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post #6 of 82 (permalink) Old 06-23-2019, 03:36 PM Thread Starter
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An update!

So I decided to go ahead and do the experiment. When planning out the plumbing I quickly realized (actually it took several hours) that I didn't need 2 buckets. I could do everything in one bucket it just meant having the pump in the same container as my lime and soil. This is just an experiment and I don't actually want plants or fish in the bucket "aquarium".

So with that in mind I went to the hardware store and bought some pellitized lime, 2 pool skimmer baskets, and some skimmer socks. I thought I already owned some potting soil but the only stuff I currently have is for cactus. So I will need to buy a small bag of potting soil next trip to the hardware store. In the meantime here is what everything looked like.



Next I put a small amount of lime into a skimmer basket with a sock.



I tried to wash the lime in this configuration but realized I was going to dissolve all of it this way since the lime is designed to dissolve into soil. I decided to just put in the bucket of water. If this works in the future a followup experiment will need to be done with actual limestone, which I could not find at my local hardware store, as this stuff clouds the water something fierce (frankly to be expected given what it is and what it is intended to do).

After that it was just a matter of setting back up the previous reactor experiment to dissolve some air into the water. Here is what that looked like:



I filled the bucket up last night and let it sit over night before doing the experiment this morning. Initial water parameters this morning were:

Ph: 7.8
Ammonia was between 0 and .26
GH 75
KH between 0 and 40
CO2 was somewhere around 1 to 2ppm.

I am going to let this run for at least 10 hours or so and then test C02 again. I will add soil probably tomorrow sometime and see how things go. I have no idea how long I would need to let it run with soil before there is any chance of seeing C02. I imagine a while since I need things to start decomposing. So at least several days.
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post #7 of 82 (permalink) Old 06-24-2019, 08:11 PM Thread Starter
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And another update!

So some progress with the expirement with a positive result????? Well... Maybe.

So I tested the water today for CO2 and it appeared as if we were now at 6ppm. I say appeared because the darn water was so cloudy it was hard to be sure. Might have been higher or lower.

I decided it was time to revamp the expirement before I went further. If this is a positive result its already useless because the water was so incredibly cloudy it could never be used in a real aquarium. I pulled the basket of pellitized lime and completely cleaned out the bucket and reactor.

Here is what my lime looked like at this point:



As you can see its sludge having completely lost all form. This did not surprise me but I had hoped the sediment would have settled out a bit. Either the current was too strong or it simply dissolved too thoroughly into the water and it was never going to clear up.

I looked online for limestone and came up with a number of options on ebay but decided I had potentially another option closer to home. A while ago I "rescued" some rocks from the harsh wilds of my local area and brought them back for possible use in a future aquarium. I really liked how these rocks looked but sadly found them reactive when introduced to some vinegar. They have sat on my patio ever since. I figured it was time to make use of them! Now I actually have no idea what these rocks are but they are definitely sedimentary in origin and are reactive. My research showed they are likely limestone of some flavor and at the least are almost certainly carbon bearing of some kind. So they in theory should work just fine. Here is a picture of what they look like:



I dumped them into some fresh water and turned back on the pump. Now I will wait another 24 hours and retest the water. If I am still seeing an increase in co2 it will be really exciting. Either way I will introduce the soil to the process at some point after that.

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post #8 of 82 (permalink) Old 06-25-2019, 03:30 PM Thread Starter
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So its been a little less then a day since I redid the bucket with my found rocks. I went out and tested the water for CO2 but it sadly showed only 1-2ppm same as my starting point. Whether this is because my rocks are not the right kind, or it just wasn't going to work with only rocks I don't know. Either way its time to add some soil to the mix and see how we do. I am going later today to the hardware store to pickup a bag of soil. I will report back once I have added it to the mix.
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post #9 of 82 (permalink) Old 06-25-2019, 07:56 PM Thread Starter
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Update!

So I bought some potting soil, here is the stuff I am using:



Its not the organic kind but I hear the whole organic thing is uneeded in tanks anyway and I really just need something carbon based to break down so this should work fine for that.

To "clean" it I put it inside 2 pool filter skimmer socks, knotted the top of the sock so I didn't have the stuff floating away, and squirted with a hose till brown fines stopped coming out. This took all of 3 minutes.



Then I put it in the bucket and wouldn't you just know, the whole thing tried to float. So I put one of the rocks ontop. Here is how it looks now:



In other news I took a ph reading and found it still to be at 7.8. This did surprise me. If I had dumped large quantities of limestone into the water and let it sit for 24 hours I really would have expected a jump in ph. I mean there has to be volume wise about 1 gallon of rock in my bucket. Sooooo about 1/5th of my volume is rock and 4/5 water. I should be seeing something I would think. This makes me believe that I do not in fact have limestone at all. Soooooo yea I need to find me some limestone or shale, or possibly charcoal.

I think I am going to buy me some proper limestone off of ebay or wherever I can find it. I apparently can not find it at my local big box hardware stores.

I may also add some plant charcoal I saw locally to me which should be another excellent source of carbon for my water.

Basically keep adding various things till I run out of ideas or get a positive result, whichever happens first ;P
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post #10 of 82 (permalink) Old 06-28-2019, 04:09 PM
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How about trying black lava rock used in grills
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post #11 of 82 (permalink) Old 07-01-2019, 03:55 PM Thread Starter
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RESULTS!

Well partial results anyway.

The experiment with dirt has been running for 6 days now give or take a handful of hours. I haven't touched it since then but the water level was starting to get low so I decided now was a good time to test before I am forced to add more water. The ph was as expected much lower then my baseline at around 7.2 and Nitrites were through the roof as again one would expect from what is essentially an uncycled tank with biological matter in it.

But most importantly I tested CO2. Results were 8ppm which is mostly good news! When I tested pellitized lime I got pretty much the same result. Now I have what I suspect are non-reactive rocks plus dirt in the bucket, and the dirt brings CO2 up to 8ppm all by itself. Does that mean if I can get my hands on some limestone I can double that number? Or does it mean that 8ppm is the max this type of system can sustain? I don't know but I am keen to find out.

My wife and I put an offer on a house yesterday which has been distracting me from the important matters of the world such as running dirt and rocks in a pumped loop in my garage, but I will try and find a source online for some limestone in the next day or so. I actually have lots of sources, I just want one to be cheap darn it.
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post #12 of 82 (permalink) Old 07-01-2019, 06:24 PM
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Quote:
Originally Posted by minorhero View Post
RESULTS!

Well partial results anyway.

The experiment with dirt has been running for 6 days now give or take a handful of hours. I haven't touched it since then but the water level was starting to get low so I decided now was a good time to test before I am forced to add more water. The ph was as expected much lower then my baseline at around 7.2 and Nitrites were through the roof as again one would expect from what is essentially an uncycled tank with biological matter in it.

But most importantly I tested CO2. Results were 8ppm which is mostly good news! When I tested pellitized lime I got pretty much the same result. Now I have what I suspect are non-reactive rocks plus dirt in the bucket, and the dirt brings CO2 up to 8ppm all by itself. Does that mean if I can get my hands on some limestone I can double that number? Or does it mean that 8ppm is the max this type of system can sustain? I don't know but I am keen to find out.

My wife and I put an offer on a house yesterday which has been distracting me from the important matters of the world such as running dirt and rocks in a pumped loop in my garage, but I will try and find a source online for some limestone in the next day or so. I actually have lots of sources, I just want one to be cheap darn it.
Much luck to you on the offer for the house.



And cool experiment you have going...


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post #13 of 82 (permalink) Old 07-06-2019, 07:12 PM Thread Starter
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Quote:
Originally Posted by Hilde View Post
How about trying black lava rock used in grills
Unfortunately I need rocks that will be reactive in an aquarium. If the aquarium water is stable then they are not dissolving in the aquarium and thus I won't get the kind of results I am looking for. Lava rock is generally very stable so I think I need to look elsewhere.


Speaking of which.. UPDATE:

So I got in the limestone I ordered from e bay. I was unable to find super cheap limestone like as in a giant sack of the stuff. I was however able to find limestone being sold as a teaching tool to geology students. The ebay business name is Geological Specimen Supply. They had the hilarious tag line of "Exporting the west one piece at a time".

Anyway the advantage of using them was that I know exactly what type of rock I bought since it came with a handy dandy card telling me:



I paid about 12 dollars for my rocks and another 12 dollars or so in shipping. Here is what they look like:



I pulled out my old rocks that I suspect are inert, and added the new limestone to the tank. About half went to the bottom of the bucket, the other half is weighing down my dirt which definitely still wants to float. Here is what that looked like after I topped off the bucket with some fresh water:



Before adding the rocks and freshwater I did another test to see where the water parameters are at.

PH: 6.8-7.0
KH: near 0
Nitrite and Nitrate: Off the chart
CO2: 8-9ppm

So now we play the waiting game. I am bad at the waiting game. I will likely get impatient and test again tomorrow.

I have no idea how long this will take but I would consider this entire thing a gigantic success if I can get CO2 up to 15ppm. At that point we are at a level where some people purposely run their tanks if they are keeping shrimp. More would be better of course but I don't know if more is feasible with the quantities of soil and rock I have. If I obtain 15ppm I will need to start modifying the experiment from the wacky system I have now into something that looks like an actual reactor you could feasibly stick under an aquarium.

Another possible advantage to using a system like this is as a means of getting fertilizers into a water supply. I have no idea how much nutrients are leaking from my soil bag but its got to be more then zero. /shrug secondary concern at best, just something I have thought about.
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post #14 of 82 (permalink) Old 07-25-2019, 06:07 PM Thread Starter
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Update!! of FAILURE!!! Or is it??

Sooo... yea I have been testing the water every few days for the past month but not only have I not noticed an increase in CO2, in the past week or so I have noticed a decrease in CO2 from 8ppm to about 5ppm. This strongly implied to me that the CO2 producing life time of the soil was around 3 weeks or so in its prime.

Overall the whole thing was looking to be a bit of a failure. I decided to change up the expirement a bit by adding a larger air pump to the process. I bought one of these things and installed it yesterday. It advertised producing 380 gallons of air per hour which sounded like a lot to me. I installed it in place of my tiny Whisper 40 and noticed the output to be significantly greater then the Whisper 40. My reactor handled the additional load with not a single issue whatsoever. Not a bubble to seen.

Wow what a great reactor I made. I pat myself firmly on the back and walk away.

I re-test the water late last night and notice not a single thing different. Still at 5ppm CO2. Well crud.

Then I get to thinking. Is my reactor actually that good? You know I never bothered to see if the air is getting into the reactor. I have no way of seeing into my reactor so I can't actually watch what is happening. But the only thing that is between my air pump and the reactor is... the check valve.

The nice brass check valve I sprang for instead of the cheapy plastic check valves. In fact it is this check valve!

So I pull the airline hose off the reactor and wouldn't you know it.... no air... not a bit. Nothing is making it past the check valve. In fact nothing has ever made it past the check valve because the check valve is absolutely DOA. I know this because I removed the darn thing and plugged the airline directly into the air pump and bubbles start coming out the end of my reactor. And I never had that happen ever before strongly implying to me that this is the first time air has ever entered my reactor....!!!

Le sigh.

Anyway the experiment is now being restarted. This time with air! I have my whisper 40 back on because the air being produced by the other air pump was massive. My hope is to get some numbers that are a bit different then previous numbers. I may dredge up my previous experiment while I am at it since I clearly never properly tested whether regular air can actually increase CO2 in an aquarium.

The experiment(s) continue!
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post #15 of 82 (permalink) Old 07-29-2019, 10:03 PM Thread Starter
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IT WORKS!!


TL;DR - I obtained 17ppm CO2

Since I last posted I was finally able to obtain complete dissolution of air into my reactor. I had to cut back the air flow all the way to about 3 bubbles per second to do this. This was of course quite the blow to my ego since I previously thought my reactor capable of doing much more. Air being harder to dissolve then water I have no idea how this stacks up compared to other reactors.

Anyway after getting things dialed in I waited and did a CO2 test 1 day later and the results... 8ppm. "Well crud" I thought. That is up from before but certainly not at the desired levels of at least 15ppm. I had a lot of hope that now that I was actually involving air it would be better.

At this point I had only 1 idea left. My thought for a while has been that the soil might not be providing the best biological breakdown of matter to release carbon into the water. I have wondered if it might be better to use something more compostable. To that end I raided my fridge. I found some salad "spring mix" that was a few days past its prime. I then opened my dirt bag in the experiment and removed half the dirt. I then shoved in the salad spring mix. 3 hours later I tested the water.

Result: 17-19 ppm CO2!

This is awesome news but its only the start. Now that I have achieved a useful result I need to do a LOT more work. I now need to isolate the variables and figure out what I did right. For instance, do I actually need the limestone? When I added it I noticed no bump in CO2. Do I need the soil? It certainly raised the CO2 but is the salad mix enough? Do I need the air reactor? Its possible it does nothing after all. And finally and most important of all, how long does it last and how stable is it? If it lasts 2 days its not very useful. If it lasts a month its very useful. If its not stable its also not useful.

Next I will basically do nothing but monitor the situation and see what happens.

Still..... success!!
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