Tropical Fish Keeping - Aquarium fish care and resources

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-   -   DIY CO2 (

jaybyrd 02-08-2008 05:04 PM

Ok. I know little but am learning a bit. It seems there are many opinions on this subject.
But here is what I have discovered and if I am wrong please - people - correct me.
My supply water from Dekalb County Ga reads at 7.0ph and 1.0kh. According to the charts that would place my CO2 saturation at 3 ppm. Is this correct?
Isn't this pretty much a normal CO2 reading?
Now 2 weeks ago I took a 2 liter style bottle that was empty and drilled a 3/16" hole in the cap and squeezed a 1/4" thick 8' long tubing through just the top. I filled the bottle with water 2/3 full. Then added copious amounts of sugar and a little yeast. I knew this system would require a little maintenance from years of home brewing experience and have to add a little more sugar every few days.
Now for the clever idea for a diffuser given to me from a fish supplier working for a national company. Use a large porous style of ph enhancing rock. I used an 8 lb. mountain of a rock in my aquarium.
Now for the readings...
6.6ph and 3-4 kh. This seems to put my CO2 saturation in the water on a 55 gallon tank at 23 to 30 ppm.

Does seem correct? - So does one really need to by expensive equipment? Is this true? Or to be more precise - is it safer to by more expensive equipment?

tigger 02-08-2008 05:18 PM

I haven't checked your CO2 calcs as I don't use that method (I have a drop checker which is waaaaay easier to read!). However, I'd be wary of using rock to raise your KH, since there's an element of uncertainty there - you are hoping the rock willdo something, but you don't know how much by. I have alow KH and prefer to add bicarbinate of soda at each water change to raise by KH by a relatively fixed amount.

The problem with yeast based CO2 systems is that your levels of CO2 are inconsistent. Inconsistent CO2 levels are often blamed (by some :wink: ) as the cause of many algae problems.

On a small tank the yeast system may work fine, but in a larger tank such as yours, inconsistent CO2 along with high light would be a recipe for disaster. I say this as I have a similar sized tank and have struggled with algae down to a combination of inconsistent CO2 and inconsistent fert dosing.

If you really want the yeast based system, why not run 2 bottles and start them a week apart so that as one winds down and needs recharged, you've got the other in full flow....

jaybyrd 02-08-2008 07:50 PM

The rock added aids in ph and not kh. The algae as pointed out earlier came from my error in believing a couple of people in a couple of LFSs that sold me many doomed to die non-aquatic plants. Those are gone ( the plants ) and true aquatic plants have been installed. And the algae was most severe with these plants and no CO2.

I check my ph and kh daily - to make sure the CO2 does not cause too much trouble.

Speaking of trouble - I did initially run two containers of CO2 because of the tank size. And staged them. The ph plummeted and well I feared for the health of the fish due to the acidity of the water. I corrected the situation by removing one of the CO2 DIY canisters and adding the porous rock as a diffuser for the one container. For the last two weeks the ph has remained stable at 6.6 and kh between 3 and 4.

see chart
* -----------------------------------------------------------------------
\ pH | 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4 8.0
KH\ |
0.5 | 15 9.3 5.9 3.7 2.4 1.5 0.9 0.6 0.2
1.0 | 30 19 12 7 5 3 1.9 1.2 0.3
1.5 | 44 28 18 11 7 4 2.8 1.8 0.4
2.0 | 59 37 24 15 9 6 4 2.4 0.6
2.5 | 73 46 30 19 12 7 5 3 0.7
3.0 | 87 56 35 22 14 9 6 4 0.9
3.5 | 103 65 41 26 16 10 7 4 1.0
4.0 | 118 75 47 30 19 12 6 5 1.2
5.0 | 147 93 59 37 23 15 9 6 1.5
6.0 | 177 112 71 45 28 18 11 7 1.8
8.0 | 240 149 94 59 37 24 15 9 2.4
10 | 300 186 118 74 47 30 19 12 3
15 | 440 280 176 111 70 44 28 18 4
| CO2 milligrams/liter


tigger 02-09-2008 03:22 AM

If the PH is remaining stable, it is because of the KH. It is the KH which acts as a buffer to the PH and the rock will have raised the KH of the water, thus making a PH crash less likely. A KH of over 4 is best to have when using CO2 so the rock you've got is doing the job you need it to (although I'd still prefer to add 2 half teaspoons of bicarb to a weekly water change than have a rock in the water :P ).

When you keep measuring the KH/PH for a while, if it stays stable, then I'd maybe try the 2 canisters again to ensure you have a steadier supply.

jaybyrd 02-09-2008 07:32 AM

The rock...
Is that what the rock does chemically in the long run when added to the water? Interesting. Tigger, your explanation is very appreciated!

Could you explain some of the following, if not all of the following, not just for myself but for all others here on the forum:

1. what is the solubility rate of CO2 compared to our standard atmospheric gasses, that we have naturally occurring, in water? I understand that CO2 is 1 1/2 times heavier than our natural atmospheric gases. It seems that the ocean, for example, absorbs roughly 1/3 of the CO2 in the atmosphere. I have tried to research this part of the equation and well - I am years out of college and high school now. see

1.1. Oh yeah and if CO2 is heavier than our atmospheric air - would the released to the atmosphere bubbles not provide a steadier or more dense supply of carbon on the tank surface? When the bubble reaches the surface of the water and the gas could be mildly trapped on the water surface by the lip of the aquarium?

2. simply explain to all a simple form of bicarb all may find available...

3. Am I to understand a planted aquarium generally runs a PH rating in the mid 6's on average?

4. If the rock I added to the aquarium ( which is actually very attractive aesthetically in my mind's eye ) is raising the KH - am I getting a true reading of the diffusion of the CO2 in my tank? Are my current results in this CO2 experiment possibly close to my desired goal?

Thanks again all!


tigger 02-10-2008 04:32 AM

I'm not scientifically minded (ex-Arts student, don't you know :roll: ) so I'm not sure that I can answer your questions tbh.

1. *shrug*

1.1 *shrug*

2. Bicarb in the UK is easy to find on the Baking section of any large supermarket as it's used as a raising agent. Note that Bicarbinate of soda, in the UK at least, is not the same as Baking Soda as the ingredients are different, although the Baking soda may have Bicarb as one of the ingredients. Here's a handy calculator for figuring out how much bicarb you need to raise your KH.

3. That's something I've never heard before.

4. If the KH is stable, then I don't see why you wouldn't be. However, I believe this is one of the reason why the drop checker is becoming more popular in checking CO2. Not sure if you've seen them before, but basically a small amount of a pre-determined 4dKH solution is held in a sort of glass bubble in the tank and there's a couple of drops of PH reagent used (from a standard PH test kit which uses Bromothymol blue). When placed under the water, the checker will change colour once it reacts with the CO2 and once you get a nice healthy green colour, you know you've got 30ppm CO2 in the tank. Basically it's a permanent CO2 test by using a defined KH of 4 - because the solution doesn't mix with the water in the tank, only the CO2 you are testing with a defined reference point already. (Google imaging a drop checker will show you what I mean about the drop checker).

Sorry, not much help this!

herefishy 02-10-2008 04:58 AM

Outstanding dialogue, simply outstanding.

jaybyrd 02-10-2008 08:45 AM

Thank you tigger.
And if anyone can answer some of my questions tigger or myself cannot I am sure all would be thankful within the bounds of this forum.

Hererfishy thanks for the compliment directed towards our dialogue. I only hope the aquarium and my pets suffer outstanding results. So far thanks to many here on the forum! My plants are beginning to really excel! I will continue the photos at home and update the progress on my 'science experiment'.

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