How much variation in PH is normal with CO2 on 24/7 & KH of 4? - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 12-09-2004, 06:44 AM Thread Starter
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How much variation in PH is normal with CO2 on 24/7 & KH of 4?

Does this seem right?

Ever since I moved the aquarium on 11/21/04 I have had a real saga with water parameters. I have been unable to get my CO2 levels consistent (& hence, I've had big time algae issues). Here are some details from the past few days:

Lights always on from 7 am - 5 pm ...

CO2 on 24/7

12/5 @ 3:00 pm:
PH = 7.2
KH = 4
CO2 = 7.5 ppm
12/5 @ 8:30 pm:
PH = 6.8
KH = 4
CO2 = 19 ppm
CO2 changed to turn off/on with the lights (off at night)

12/7 @ 5:40 pm:
PH = 7.2
KH = 4
CO2 = 7.5 ppm
12/8 @ 10:30 am:
PH = 7.1
KH = 4
CO2 = 9.5 ppm
12/8 @ 4:00 pm:
PH = 7.1
KH = 4
CO2 = 9.5 ppm
Switched CO2 to be on 24/7

12/8 @ 10:00 pm:
PH = 6.8
KH = 4
CO2 = 19 ppm
So ... as you can see, the PH changes quite a bit (& quickly) when I leave the CO2 on after the lights go out. Because of the shrimp losses I had a couple weeks ago, I'm hesitant to allow the CO2 to remain on after I get those 6.8 PH readings in the late evening. In any case, I don't believe I ever had these "swings" before. The plants are doing fine, pearling, etc.

A KH of 4 isn't too low, so I don't think it's caused by low KH.

What gives? Is this normal?

John P.

Last edited by John P.; 12-10-2004 at 03:52 AM.
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post #2 of 6 (permalink) Old 12-20-2004, 08:13 PM
 
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When I left the CO2 on continuously, the pH would drop to 6.8 near the end of the dark cycle. My KH is 9, so I would say that a small increase in acidity is normal, and with a KH of 4 would expect a slightly larger increase.
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post #3 of 6 (permalink) Old 12-20-2004, 08:32 PM
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at KH of 5.5 (and pressurized co2) I get about a .05 change in pH at night, but nothing more. Therefore it stays between 6.70 and 6.75 at all times.

Do you have anything in your tank that adds to KH over time, like Limestone, Crushed Coral, or anything else? I had to take out about 50% of my CC in my Fluval due to the variations in KH over days at a time.

Edit>> should have actually asked whether or not you have re-tested KH each time you got those measurements, or if you assume it stays constant at 4.

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post #4 of 6 (permalink) Old 12-20-2004, 08:51 PM
 
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Spar, how do you measure a .05 difference in pH?
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post #5 of 6 (permalink) Old 12-20-2004, 09:09 PM
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Pinpoint Digital pH Reader. Reads in 100th's

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post #6 of 6 (permalink) Old 12-20-2004, 09:41 PM
 
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Quote:
Originally Posted by Spar
Pinpoint Digital pH Reader. Reads in 100th's
I didn't know they were that accurate. Wow, thanks Spar, now I gotta me one! .

But, back to John P.'s question, do you think there was more out-gassing when your pH was more steady? Was that before the move? Maybe the surrounding air caused more outgassing back then? I'm assuming you're still injecting the CO2 directly into your 2213, so that can't explain it. Did you change tthe position of the spray bar?

Last edited by ksand; 12-20-2004 at 09:46 PM. Reason: Afterthought
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