• For a Limited Time the R2R Partner Membership is NOW OPEN! Get some cool swag and chances to win part of over $20,000 in prizes! Click here for more details

Sudden pH drop

Privateye

Active Member
View Badges
Joined
Jan 17, 2020
Messages
133
Reaction score
87
That is only true if nitrate is accumulating. Nitrification consumes alkalinity

If nitrate is steady, there is zero effect on alkalinity because the consumption of nitrate by organisms returns exactly the alkalintiy lost in nitrification.

If nitrate is declining, then alkalinity will actually rise by that process.
I think I see what you mean, but bear in mind that denitrification could also be responsible for stability in nitrate. Many of us have active denitrification in our systems due to anoxic zones and bioavailable carbon/sulfur. Zooxanthellae also consume some. My tank never deviates from 0-5 ppm nitrate, even with water changes every 2 months. Back when I worked at a large fish farm, we ran denitrifiers 24/7 to keep it below 200 ppm.

And to mass-balance, denitrification restores 50% of the carbonate lost through nitrification. So you would still have a net loss over time. I once argued for a point on a fish pathology class test in grad school because I claimed that denitrification is a source of alkalinity. They gave me the point, but made sure to mention the mass balance. An alkalinity test report might put this issue to bed though!
 

Brew12

Electrical Gru
View Badges
Joined
Aug 14, 2016
Messages
22,013
Reaction score
58,960
Location
Decatur, AL
Holy cow, YES! I took out half of Cheto this morning! Is that it? I have done that many times before!!
I see a pH drop when I pull cheato, but I normally remove a lot more than half. I suspect it could be the issue. Might be a perfect storm with pulling the chaeto and the skimmer going off line. Less chaeto to turn CO2 into O2 and less air exchange with the skimmer not running. Seems plausible.
 

Brew12

Electrical Gru
View Badges
Joined
Aug 14, 2016
Messages
22,013
Reaction score
58,960
Location
Decatur, AL
I think I see what you mean, but bear in mind that denitrification could also be responsible for stability in nitrate. Many of us have active denitrification in our systems due to anoxic zones and bioavailable carbon/sulfur. Zooxanthellae also consume some. My tank never deviates from 0-5 ppm nitrate, even with water changes every 2 months. Back when I worked at a large fish farm, we ran denitrifiers 24/7 to keep it below 200 ppm.

And to mass-balance, denitrification restores 50% of the carbonate lost through nitrification. So you would still have a net loss over time. I once argued for a point on a fish pathology class test in grad school because I claimed that denitrification is a source of alkalinity. They gave me the point, but made sure to mention the mass balance. An alkalinity test report might put this issue to bed though!
You guys know much more about this than I do, but I was under the impression this was a process that took days, not hours. Can you help clarify that? I'm always up for expanding my knowledge.
 

Privateye

Active Member
View Badges
Joined
Jan 17, 2020
Messages
133
Reaction score
87
You guys know much more about this than I do, but I was under the impression this was a process that took days, not hours. Can you help clarify that? I'm always up for expanding my knowledge.
Your are 100% correct I think. Check that graph again. I think it's a week span unless I misread or something. Those daily swings were the indicator for me. Just a misunderstanding!
 
Zoanthids.com

Brew12

Electrical Gru
View Badges
Joined
Aug 14, 2016
Messages
22,013
Reaction score
58,960
Location
Decatur, AL
Your are 100% correct I think. Check that graph again. I think it's a week span unless I misread or something. Those daily swings were the indicator for me. Just a misunderstanding!
I should have been more clear. The pH was going down 0.05 per day, and I didn't think biomass could have that much of an impact. But, I say that will little confidence. I thought with biomass uptake you wouldn't see a measurable difference for a week or more.
 

Privateye

Active Member
View Badges
Joined
Jan 17, 2020
Messages
133
Reaction score
87
I should have been more clear. The pH was going down 0.05 per day, and I didn't think biomass could have that much of an impact. But, I say that will little confidence. I thought with biomass uptake you wouldn't see a measurable difference for a week or more.
A fair point. That may be but I'm not familiar with those limitations. Do you have a source? I dealt with massive biomass so 0.05 in a day was nothing. However, in my aquaculture experience it was freshwater and nitrifying bacteria were basically r-selected. As a reef hobbyist, I lose 0.5 dkH per day in 90 gallons. I suppose it would be less is my dkH were lower. I keep 8-9.
 

Brew12

Electrical Gru
View Badges
Joined
Aug 14, 2016
Messages
22,013
Reaction score
58,960
Location
Decatur, AL
A fair point. That may be but I'm not familiar with those limitations. Do you have a source? I dealt with massive biomass so 0.05 in a day was nothing. As a reef hobbyist, I lose 0.5 dkH per day in 90 gallons. However, in my aquaculture experience it was freshwater and nitrifying bacteria were basically r-selected.
I don't have a source, which is why I lack confidence in that statement. It is only a perception that I have, but can't claim it is an accurate perception. I am honestly just trying to learn more, not trying to challenge.

I drop over 4dkh per day in my 187g system but I have no way to quantify how much is coral and biomass. I find this very interesting, but challenging to expand my knowledge.
 

Privateye

Active Member
View Badges
Joined
Jan 17, 2020
Messages
133
Reaction score
87
I don't have a source, which is why I lack confidence in that statement. It is only a perception that I have, but can't claim it is an accurate perception. I am honestly just trying to learn more, not trying to challenge.

I drop over 4dkh per day in my 187g system but I have no way to quantify how much is coral and biomass. I find this very interesting, but challenging to expand my knowledge.
Hey, even if you were challenging, no worries! I want to learn here too and this trade is mostly about experience. Holy moly 4 dkH!? That's incredible, but literally credible. I'll bet you have very good growth. A calcium reactor too or some dosing pumps that you have confidence in. I'm at the dosing pump level myself. I feed 1 cube per day, 5-6 days per week, for 5 small fish.

And I digress, but to the OP let's get an alkalinity reading. It's a huge piece of this puzzle.
 
Last edited:
OP
arvind

arvind

Active Member
View Badges
Joined
Dec 21, 2013
Messages
171
Reaction score
43
Location
United States
Here is some background info that I neglected to mention. Trying to bring my high alk from 9+ to 8. It went from 9 to 7.17 in less than a week.

SmartSelect_20200926-084518_Chrome.jpg


I was too focused on what happened on one day and trying to relate things that I did on that particular day and completely ignored the fact that it was a result of what has been happening over a week. Now I realize that I need to stabilize my alk and that will in turn stabilize the pH. Apologies for not bringing this before, a newbie mistake.
 
Best reef aquarium LED lighting

What's the first thing you do when you see algae forming in your tank?

  • Panic and freak out

    Votes: 37 6.7%
  • Identify it as best you can

    Votes: 165 30.0%
  • Test your water

    Votes: 175 31.8%
  • Pull it out

    Votes: 69 12.5%
  • Order more clean up crew

    Votes: 53 9.6%
  • Other (please explain)

    Votes: 51 9.3%

Online statistics

Members online
1,104
Guests online
2,936
Total visitors
4,040
Top