A Question On The Co2 Ph Drop

Bishop

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Short summary is that my rested PH from tank after 24 hours reads 7.10 PH.
But my tank before Co2 turns on reads 6.15 PH, both measured digitally and fluctuations over the months are less than 0.10 Ph.

Fish gasp at about 5.45 with light surface movement and skimmer.
Current Ph sits at around 5.5 - 5.55 at its lowest and 16 hours later when co2 turns on again its barely increased by .5

Is this just excess Co2 that the system can't off gas. It seems like a lot and I am wondering of there is some underlying cause or
Other things playing a role in the water column.?

I have really struggled with Co2 on this new tank which has helped me learn a heap but I inject it to the point where I can't inject any more and still have plants melting and other low co2 issues, so can't yet rule out having good co2.

Any thoughts?
 

rajkm

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CO2 levels are higher in tank at night because even plants add to CO2. When you let the water sit outside the tank, you take out that equation. After that, the carbonates also play a role in balancing the ph in water with fixed acid levels.

So I would use the ph of water sitting in the glass and then aim for a 1.2-1.3 ph drop which in you case is more than that. Now if your plants are happy at 5.5 and fish are happy too, then I would leave it. I could however think that you will be ok at 5.8, as long as your carbonates are at same levels all week.

If you are worried about night time ph, you can either increase surface agitation or add a air bubbler on timer to help degas water overnight. But I would not worry about it.
 

Bishop

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If you are worried about night time ph, you can either increase surface agitation or add a air bubbler on timer to help degas water overnight. But I would not worry about it.

I'm always gona worry cause I don't understand :D But essentially all I am trying to do is rule out co2 as an issue or make it non limiting.
I do run surface agitation and a skimmer and the co2 is off 2 hours before lights out.

Have noticed a change over last week though after I did a massive trim of plants, so you might be on to something there.


How old is your tank ?
About 6 months.
It's well maintained. To the point at least that I am trying to maintain it well if that means anything.

I noticed a small amount of diatoms today, so maybe the bio filtration stalled and struggled at 5.5 ph but also trimmed and replanted nearly everything so will give it some time to stabilize and see if it continues.
 

Phishless

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Short summary is that my rested PH from tank after 24 hours reads 7.10 PH.

I would test de-gassed water with an air stone in it after a half hour.

Is this just excess Co2 that the system can't off gas.

Could be an excess?
Keep in mind both CO2 & O2 can exist the water @ the same time.
During the photo-period are your plants pearling?
If so this is a sign the water column is saturated with O2, a good thing for sure.
 

Bishop

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I would test de-gassed water with an air stone in it after a half hour.
Is there a difference between the two? I don't have an airstone. But can run a little pump in a bowl probably

During the photo-period are your plants pearling?
If so this is a sign the water column is saturated with O2, a good thing for sure.

Plants are pearling well, towards end of cycle everything is covered in large bubbles.

Just not heard of a tank gassing off so little co2, I thought maybe there was something else at play.