How long before pressurized Co2 changes the PH? - The Planted Tank Forum
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post #1 of 16 (permalink) Old 08-23-2009, 02:30 AM Thread Starter
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How long before pressurized Co2 changes the PH?

Well I just got my Co2 injection system hooked up and running yesterday. got a 10lb tank with a Rex regulator with a Red See reactor. The reactor at first displayed a "tornado" inside the chamber but now doesn't show anything inside it. I have about 3 bubbles per second right now going.

Anyways I found my tests to be kind of surprising today.
My test results a week ago (dosing flourish excel) with no pressurized Co2
Ammonia 0
Nitrite 0
Nitrate 0
Ph 7.6
KH 126
GH 232
Which was 5.35 ppm carbon for my 30 gallon, a bit low.

Now today I tested again having the Co2 running since last night and it's had all day to run.
Ammonia, nitrite, and nitrate all 0
PH 7.6 (unchanged, expected to see at least a slight drop)
KH 89.5
Gh 230
Which results in only 3.7ppm carbon.

So yeah, bit confused on why I have a lower carbon reading AFTER hooking up a Co2 injection system. Does it take a few days for it to show up in the water chemistry? Should I crank up the Co2 more?

The tests where with liquid drop tests so as far as I know they are very accurate.
Any tips would be great!

After thinking about it for a minute...in regards to there being no tornado in the reactor...it seems the reactor needs a certain amount of co2 input to keep a steady vortex. Now I put it up to about 5 bubbles or so a second and it's keeping a steady vortex. But on the other hand with 3 bubbles per second there was no vortex after a while BUT I didn't see any Co2 bubbles escaping so I assume it was getting mixed into the water. Just a thought. Maybe I'm overthinking this and just need to give the system some time to do it's job. Not sure if I should expect any changes in just one day.

Last edited by qwiksilvertrav; 08-23-2009 at 02:42 AM. Reason: thought of a possilble solution
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post #2 of 16 (permalink) Old 08-23-2009, 02:36 AM
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did you check for any leaks on the reg, co2 line, etc?


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post #3 of 16 (permalink) Old 08-23-2009, 03:23 AM Thread Starter
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Yes I went over the system and can't feel any leaks anywhere. Used all of Rex's good tubing etc.
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post #4 of 16 (permalink) Old 08-23-2009, 03:46 AM
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Do you use an airstone in the tank? Do you use a hang on back filter? Is the water surface heavily rippled by water flow? Does the tank have a lot of fast growing stem plants? How is the flow from the reactor released onto the tank? I'm looking for possible reasons for you to lose CO2 at the water surface, or to fast growing plants, faster than usual.

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post #5 of 16 (permalink) Old 08-23-2009, 03:59 AM Thread Starter
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Sorry I should've included some more information. I have no airstone and the surface of the water is quite calm. I have a canister filter with the spray bar a ways under the surface. The reactor I have is a RedSea CO2 Reactor 500.
There really isn't anyway for the Co2 to escape from what I can see.

For stem plants I have some Anacharis as some background plants and some Ludwigias in the front of the tank.

For now I turned up the Co2 up a tad and noticed that there's a visible vortex in the reactor now which wasn't the case before.
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post #6 of 16 (permalink) Old 08-24-2009, 12:16 AM Thread Starter
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Did another test today and it went up *slightly*. It was now at 6.5 degrees which resulted in 4.8ppm. Ph remained the same.
Now I was expecting my PH to drop and my carbonate to go up but I'm not seeing this. Does this process just take time? I'm running 5 bps or so and I do not see ANY bubbles coming out of the reactor. I mean if Co2 was escaping I would see it. I'm guessing I may have a leak somewhere.

I checked the system and pulled off the hose after the bubbler. There is zero notable air flow after the bubbler. Is this normal? I don't feel any air coming out of the bubbler at all. Now of course when the Co2 bubbles through the water it slows down the air flow or something, but is this my problem (having the bubbler incorrectly installed)?
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post #7 of 16 (permalink) Old 08-24-2009, 01:25 AM Thread Starter
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Well found a leak at the check valve and fixed it....bubbles started shooting out of the reactor! Turned it down a tad, waited an hour, and tested again. Wow, ph went from 7.6 to 6.6 or 6.8 and KH remained the same. Turned down the bubble rate a bit. Think I have my Co2 working now. lol
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post #8 of 16 (permalink) Old 08-24-2009, 01:33 AM
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It's always a leak that gets most people

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post #9 of 16 (permalink) Old 08-24-2009, 01:40 AM
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Yeah, your kh should stay the same however. Co2 alone wouldn't affect that, plants using the minerals or if you had a bunch of mts maybe. The carbon your putting in your tank (co2) is not the same as a what your testing for in a carbonate hardness test. Anyway good job finding your leak and good luck with your tank.


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post #10 of 16 (permalink) Old 08-24-2009, 02:02 AM
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What usually fools us, and certainly fooled me, is that the leak rate that is enough to virtually eliminate the CO2 going to the tank, is so small we often miss it. I found that I had to leave soapy water on my connections for several minutes, then return and look for mounds of tiny bubbles at a connection. Only after that was I able to find my leaks and eliminate them. Our CO2 flow rate would be called zero by most people who use pressurized gases - it is that small.

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post #11 of 16 (permalink) Old 08-24-2009, 03:09 AM Thread Starter
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Alright good to know! Co2 is definitely working now.
I just tested now before the system goes off for the night and my PH reached as low as 6.4 with 6 degrees of KH. I turned it down after the last test to 1 BPS since I overshot my ideal level by quite a bit. Kinda scary my PH went from 7.6 to 6.4 in just over 2 hours. My 5 Oto's seem just fine though.
I'm using this to determine what the carbon ppm is http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
Basically according to this calc it says I was up to 71 ppm!
I'm going to keep it at 1 BPS and test it again when I get home from work tomorrow (it'll be on for about 4 hours by that time).
Is my method of testing the carbon ppm a solid and reliable method? I suppose I should simply invest in a drop checker soon.

But according to that calc my target PH should be 7.0 - 7.2 with the KH I have. What exactly affects KH in changing if it's not the carbon I'm putting in? Thanks for the input so far.
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post #12 of 16 (permalink) Old 08-24-2009, 03:18 AM
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No, the ph/kh method is not reliable. Yes get a drop checker, it'll be one of your best investments. An example of how the ph/kh isn't reliable could be viewed in a post i had made the other day, because I had been having co2 problems myself.

https://www.plantedtank.net/forums/ge...s-what-am.html

For example in my tank, my ph is usually around 6.4, but my kh is through the roof, 21 dKH, or about 378 ppm. The chart your referring to would tell you that i have nearly 300 ppm of co2, but I assure you, i definitely do not . In fact, my co2 has been low, so i've been having problems with algae.. among other things.

kh is affected by minerals in your water, calcium and magnesium. a higher kh generally helps prevent your ph from dropping drastically, which would be why your ph dropped more then a full degree from your co2. not a bad thing, just something to keep an eye on

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Originally Posted by qwiksilvertrav View Post
Alright good to know! Co2 is definitely working now.
I just tested now before the system goes off for the night and my PH reached as low as 6.4 with 6 degrees of KH. I turned it down after the last test to 1 BPS since I overshot my ideal level by quite a bit. Kinda scary my PH went from 7.6 to 6.4 in just over 2 hours. My 5 Oto's seem just fine though.
I'm using this to determine what the carbon ppm is http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
Basically according to this calc it says I was up to 71 ppm!
I'm going to keep it at 1 BPS and test it again when I get home from work tomorrow (it'll be on for about 4 hours by that time).
Is my method of testing the carbon ppm a solid and reliable method? I suppose I should simply invest in a drop checker soon.

But according to that calc my target PH should be 7.0 - 7.2 with the KH I have. What exactly affects KH in changing if it's not the carbon I'm putting in? Thanks for the input so far.


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post #13 of 16 (permalink) Old 08-24-2009, 03:34 AM Thread Starter
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Great thanks for the quick post! I'll order one up right now.

Also on a good note, my plants are all pearling like crazy now. ALL of them are literally coated in bubbles!!! Which was nonexisent previously.
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post #14 of 16 (permalink) Old 08-24-2009, 03:55 PM
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The pH drop due to CO2 is not harmful to the fish. It isn't pH that fish are bothered by, but the KH and/or total dissolved solids in the water. When CO2 is not being used, a big pH change means some kind of salt has built up in the water (or been removed). That does affect the fish. Everyone who uses high light (high tech) and CO2 will very likely shut off the CO2 at night, and will have enough surface ripple going to eliminate much of the CO2 in the water every night. Those people have a pH change of about 1 or more (pH 7 to 6, for example) going on every day, and none will have fish problems as a result. You can't even drop the pH enough to harm the fish, just by adding CO2. The lowest pH you can get with CO2 is around 5.5, and before you can reach a too low pH you will have killed the fish with CO2 poisoning.

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post #15 of 16 (permalink) Old 08-25-2009, 04:12 AM Thread Starter
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Alright thanks for the explanation on that. Today the PH got to it's lowest of a 6.5. In This morning it had climbed back up to a 7.0 or so. Originally it had started at 7.6.

Is it a good practice to maybe have an airstone kick on after the lights and Co2 go off to replenish the water with Oxygen? Right now I have very little surface agitation (besides some light waving from the currents below) as I didn't want Co2 escaping.
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