CO2 degassing & ph

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tackful

AC Members
Mar 15, 2007
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Sausalito, CA
Hi,
Wonder if some members could help me with a small concern. During co2, the tank is at 6.4, but rises no further than 6.6 during the off period. As a reverence, the tank water rises to 7.6 when left out for 48 hrs. Fish seem fine, eating well and never going to the surface during the on period, but I wonder if this is still a bit of stress for them as II do have occasional fish losses. The filter outflow causes mild surface movement, but no splashing. Appreciate any ideas.
 

dougall

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Mar 29, 2005
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Have you measured hardness or CO2?

How are you measuring pH and have you considered a second opinion?

Anything in the aquarium that would increase water hardness?
 

tackful

AC Members
Mar 15, 2007
628
11
18
Sausalito, CA
kh =4, and gh =5. The large piece of driftwood has been in the tank for years. Otherwise, just fish, plants, and the Eco-complete substrate (w/2 root tabs), Measuring ph with an API kit. According to my hardness and ph, I'm at around 30 ppm c02 when it's on.
 

dougall

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Mar 29, 2005
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As long as the fish aren't gasping at the surface just before CO2 turns off (assuming it's controlled with a simple solenoid and timer) I wouldn't be worried about stress, the change in pH is going to stress them if the change is due to changes in hardness not CO2.

Driftwood won't increase hardness.. that might be carbonate holding rocks, or substrate (or crushed coral in the filter) but I was most worried about the change in pH from the height of CO2 injection to off-gassed I ernight .

But it's about a point, which corresponds to 30ppm too.

Remember plants will respire CO2 while not photosynthesizing too, so it won't drop overnight as much, and if anything you want the amount to not increase too much overnight.

I would relax, I don't see any problem.
 

dougall

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Mar 29, 2005
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Yeah,fine..

I was originally concerned because if the change based on the water sitting overnight..

The change in the tank itself is minimal and really no cause for concern . Folks likely see bigger swings with water changes and it's normally a swing that is a cause for concern

Unless your fish actually show something concerning I normally don't pay close attention to the numbers
 

FJB

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Jun 7, 2019
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The OP does talk about frequent fish loses. I don’t know why.
Agree that 6.4 to 6.6 is not a major pH change. However, the op also talks about changes from 6.4 to 7.6. Don’t forget the pH scale is logarithmic. A change of 1 unit (say 6 to 7) represents a 10 fold difference in the concentration of H+ ions. That is a big change, not the best idea. I wouldn’t be running a tank like that, although some fish can adapt if gradual. However not healthy in the long term.
 
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dougall

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Mar 29, 2005
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The increase to 7.6 was aquarium water left out of the aquarium overnight .. or so I thought

My money is in any losses being due to a reason other than CO2, at least based on the information given.


Maybe a second opinion of all test results would be a good idea, but if they are pretty accurate then the CO2 injection seems absolutely normal
 
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