DIY CO2 for my 75 gallon - Build Thread / Performance Updates
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Old 06-12-2014, 01:22 PM   #1
burr740
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DIY CO2 for my 75 gallon - Build Thread / Performance Updates


Decided to hook up a bit of CO2 for my 75.

Not sure if I actually want CO2 on this tank or not, but I have been thinking about it. So before investing in a pressurized system, I decided to hook up a bit of DIY to see if I can get a feel for how things react.

Im aware of the challenges when it comes to DIY on larger tanks. Im just hoping to get a consistent 15 or so ppm - using minimal bottles. I believe that is possible with a leak free system and good diffusion.

Ive been experimenting for a few months on a 20 gallon using a single 2L bottle. I found that the following recipe will run 16-17 days, before starting to slowly taper off. After 3 weeks, it's still generating a lot, just not as much as originally, like 2 bubbles every 3 seconds instead of 1 per second.

So considering a duration period of ~2 1/2 weeks, before a slow decline, I decided to start out with three 2L bottles. The plan is to change out 1 bottle every week. Im willing to go to four and change two/week, perhaps using a bit more yeast, but Im hoping that wont be necessary.


The Simple Recipe:
2 cups sugar
1/2 TBS regular baking yeast
1 TBS baking soda

I activate the yeast first in a small bowl of luke warm water. Sprinkle in a tad of sugar and stir it gently with a fork. Then let it sit for about 15 minutes, stirring it again every 5 minutes or so. In the meantime I mix up the sugar/soda/water in the 2L bottle. I fill it about halfway with room temp water and shake it up well. Very well. Then fill it the rest of the way up (to just above the top of the label) and shake it again until everything is dissolved good. Then I pour the yeast mixture in. I dont shake it up any further.


Now on to the build pics...

Here is the finished gas separator, a 1.89L Juicy Juice bottle with a big wide cap. That was important because I wanted the lines going in separately, to be able to tell exactly what each bottle is doing.




To create the seals, I used a combination of check valves, and air tubing connectors, the kind that come with those cheap discard-a-stone diffusers, like you see in the picture ^.

It is based on the following method (Thanks to DarkCobra, who I believe originally came up with it some time ago)





15/64" hole
Push tubing through
Insert the connector, which expands the tubing in a tapered manner
Push it back into the cap, HARD

100% mechanical. No mess. No leaks.


Finished separater top:




Finished reactor bottle cap:




All hooked up:

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Old 06-12-2014, 01:24 PM   #2
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Diffusion is kind of a two stage event. First there's a piece of regular cotton ball packed tightly into the CO2 line, which then runs into the intake of a small, upside down power head.








Hard to tell in the pic because my light is aimed mostly toward the back, but the power head is mounted at the very front of the tank. The bulk of the mist stream hits the ground about where the center Crypt is, and then sorta just disperses all over. I think it is pretty efficient. You can barely see any bubbles unless you get right up close. Then it looks like a Sprite can exploded in there.

It's been running now for two days. Already seeing a bit of pearling, mostly from the Ludwigia and Bacopa. I only have med light (2 T5HO) so Im not really expecting to see much. Everything seems to have really perked up though, that much is obvious. Tops of the Mermaid Weed turned a different color virtually over night.




I havent done a full Degas test with the same water yet, but PH seems to be down about .7 from what it normally is (taken in the middle of photo period) Correct me if Im wrong, but that's like low 20's ppm? If so that is fantastic. I'll know more in 24 hours.

Also ordered a glass ADA drop checker from Amazon, apparently gonna be 2-3 weeks before it arrives though :/
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Old 06-12-2014, 02:52 PM   #3
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it will help but with a tank that size you will want a bottle soon i did diy for a good 90 days it was fun but then mixing every week sucked.
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Old 06-12-2014, 02:54 PM   #4
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The little bottle isn't going to add much CO2 in a 75G. The 3 bottles is best for a 30G. Maintaining them will be a pain.

Your plants look great with what you have now so the bottle might give them a little extra CO2.
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Old 06-12-2014, 03:16 PM   #5
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awesome!!! how did you maintain such healthy plants without CO2? I am a newbie and from what I am finding so far, lighting and CO2 are what we need to get a beautiful tank like yours.
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Old 06-12-2014, 03:24 PM   #6
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Quote:
Originally Posted by FishieNewbie View Post
awesome!!! how did you maintain such healthy plants without CO2? I am a newbie and from what I am finding so far, lighting and CO2 are what we need to get a beautiful tank like yours.
Thanks. The main thing I did was spend a lot of time reading this forum!

Lighting is obviously important, but most important is to have the right amount, as in, enough but not too much. Tons of plants out there that will thrive under low to medium lighting (what I have) and no CO2.

Check out this thread there are hundreds of examples- Low -Tech Show and tell
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Old 06-12-2014, 07:56 PM   #7
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A 0.7 drop in pH due to CO2 means the ppm of CO2 in the water went up by a factor of 10 to the .7 power, or about a factor of 5. Assuming the water had 3 ppm before the CO2 was added, you would have about 15 ppm of CO2 now. For low medium light that may be all the plants can use. But, I don't recall anyone reporting on test results to see what ppm of CO2 is optimum vs light intensity. It would be an interesting test to try, but difficult to do well.
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Old 06-12-2014, 09:55 PM   #8
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Thanks for the info, Hoppy. Around 15 ppm is the target range Im shooting for, consistently of course. I arrived at the low 20s going by this bottom right chart, which seems to use a slightly different multiple somewhere.

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Old 06-13-2014, 11:03 PM   #9
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Before I went fully pressurized this is almost exactly what I had set up for my 29G. At that rate you will have a pretty steady flow of CO2. It did not strike me as being particularly difficult to keep up with changing out one bottle every weekend while I was doing other tank maintenance. By doing it this way you always have at least 2 bottles pushing a good amount of CO2 and by using the check valves for each bottle, you don't lose any time regaining pressure from a swap.
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Old 06-14-2014, 04:17 AM   #10
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Quote:
Originally Posted by burr740 View Post
Thanks for the info, Hoppy. Around 15 ppm is the target range Im shooting for, consistently of course. I arrived at the low 20s going by this bottom right chart, which seems to use a slightly different multiple somewhere.

That bottom right chart is incorrect. It assumes that the ppm of CO2 is directly proportional to the pH drop, and it is actually proportional to 10 to the pH drop power. A .5 drop in pH actually means about 9.5 ppm of CO2.
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Old 07-10-2014, 02:27 AM   #11
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Thought I'd post an update, since it's been about a month. Still running 3 bottles, changing 1 per week. Plants have really exploded. Im having to prune the ludwigia and bacopa every week because it hits the surface. Drop checker stays a relatively darkish green, slightly brighter when the lights first come on.

Between that, degas test, ph/kh chart, Im fairly confident in a ppm of at least 15, maybe a tad higher. Regardless, it's made a huge, HUGE difference in the growth rates and color of things.

Here's a couple pics. Ive re-arranged the tank some since the last ones.



Drop checker at the end of photo period. Picture-wise it's a fairly accurate color representation, maybe a shade lighter in person.

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Old 07-19-2014, 01:58 AM   #12
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Here's a little growth update, 9 days since the last pics.



Gonna have to bush hog the back right corner pretty soon. I cut the Bacopa back a few days ago. It had hit the surface to the point it was shading the L Glandulosa.

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