Sudden pH drop

[Delapool]

When you're at a KH of 0, you have no CO2/bicarbonate buffer. So the addition of an acid will easily lower your pH, and the addition of a base will easily raise your pH.



A KH of 0 has no relationship to a neutral pH of 7.0. KH is a measurement of your tank water's resistance to pH change, and that's it.



If you want to see the relationship between buffer concentration and pH in mathematical form, you can check out the Henderson-Hasselbalch equation.

Appreciate the reply. The link didn't help much unfortunately as I don't do much chemistry maths. Was there a bit in the link to concentrate on?

I was thinking though that pure water would be at ph of 7 and since it is pure kh would be 0?

Say at that point we lift kh, ph would also lift as H+ is consumed. So the kh is not only resisting change in ph but causing change in ph as well.

Then it seems to me that the more acid a ph, the more kh is used up trying to resist the low ph. So if pure water is in balance at ph of 7, below 7 kh would get used up resisting the ph decrease. It might take time but all the kh would go.

What am I missing? I've been using this link below for reference in case that helps. I understand certain kh buffers will result in a certain ph, what I think I'm missing is what happens in the absence of any kh buffer to ph and when that point in ph will be reached.


http://www.cichlid-forum.com/articles/gh_kh_ph.php

Edit - apologies for the left turn for OP, if this is off track just let us know.

 

[Caliban07]

Hi delapool try this simplified article.

http://www.mankysanke.co.uk/html/understanding_buffering.html




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[PNWaquarist]

I was thinking though that pure water would be at ph of 7 and since it is pure kh would be 0?

Pure water is pH 7 in theory. In reality, it's about pH 5.5 because carbon dioxide from the atmosphere dissolves into it and forms carbonic acid.

If one were able to isolate that water from the atmosphere and no CO2 dissolved into it, it would be KH 0. On the other hand, it is possible to have pH 7.0 water with a high KH value. In this case, the conjugate acid and conjugate base concentrations of the buffer are in the correct ratio to give a pH 7.0 solution.

Say at that point we lift kh, ph would also lift as H+ is consumed. So the kh is not only resisting change in ph but causing change in ph as well.

That depends which part of the KH you're lifting: the conjugate acid or the conjugate base. Read about buffer solutions here.

If you add carbonate or bicarbonate ions to a pH 7 solution in an attempt to raise the KH, you'll increase the pH. This is because carbonate and bicarbonate are bases. On the other hand, if you do a carbon dioxide injection into your tank to try to raise the KH, the CO2 will react with water to form carbonic acid. This will lower your pH.

Then it seems to me that the more acid a ph, the more kh is used up trying to resist the low ph. So if pure water is in balance at ph of 7, below 7 kh would get used up resisting the ph decrease. It might take time but all the kh would go.

This is true. If you add a lot of acid or base to a buffered solution, it will eventually "use up" all of the buffer and the pH will decrease (or increase) to the point where the buffer no longer works.

What am I missing? I've been using this link below for reference in case that helps. I understand certain kh buffers will result in a certain ph, what I think I'm missing is what happens in the absence of any kh buffer to ph and when that point in ph will be reached.


GH, KH, and pH for the Advanced Hobbyist

Edit - apologies for the left turn for OP, if this is off track just let us know.

I don't have time to read the full link. It sounds like you're on the right track, though. Doing a Google search on acid-base equilibria and buffers will probably lead you to web sites that explain the chemistry better than a fish-related site.

 

[Delapool]

Ok, thanks - some late night reading to do

 

[Jessy2363]

I add baking soda to my tank to up the ph. I mix it first in a cup of water first then tip it in in random spots to avoid the mic touching the fish before it gets diluted.
I add 1 teaspoon per 10 gallons. If the ph is super low. Like below 6. But if it's just slightly dropped I add just a tiny bit. You can't mess up if you add too little. Also if your tank is getting ammonia spikes from old tank syndrome that can cause the ph to drop. Too much toxic bacteria can cause a drop in ph. And if the ph drops then the good bacteria can't grow properly because it needs a ph of around 7 or more to be fully sustainable.
Don't let your ph drop to low otherwise the tank might need to be recycled. Not to mention it won't be able to cycle properly with such a low ph.

I am pretty sure new tank syndrome is from a build up of toxins in the gravel. Don't quote me on that...

I put crushed coral in my filter to buffer it once I had added the baking soda. If you can't find crushed coral then I think crushed shells can also be used as a buffer.

Personally I would vacuum the gravel and get rid of all the old tank syndrome gunk. Then is rinse the filter media in tank water to ensure not to kill the beneficial bacteria. Then i'd up the ph to about 7.6 with baking soda and use prime if ammonia or nitrites spike. Hopefully it will recycle and have a fresh start.





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[gilpi]

I add baking soda to my tank to up the ph. I mix it first in a cup of water first then tip it in in random spots to avoid the mic touching the fish before it gets diluted. I add 1 teaspoon per 10 gallons. If the ph is super low. Like below 6. But if it's just slightly dropped I add just a tiny bit. You can't mess up if you add too little. Also if your tank is getting ammonia spikes from old tank syndrome that can cause the ph to drop. Too much toxic bacteria can cause a drop in ph. And if the ph drops then the good bacteria can't grow properly because it needs a ph of around 7 or more to be fully sustainable. Don't let your ph drop to low otherwise the tank might need to be recycled. Not to mention it won't be able to cycle properly with such a low ph. I am pretty sure new tank syndrome is from a build up of toxins in the gravel. Don't quote me on that... I put crushed coral in my filter to buffer it once I had added the baking soda. If you can't find crushed coral then I think crushed shells can also be used as a buffer. Personally I would vacuum the gravel and get rid of all the old tank syndrome gunk. Then is rinse the filter media in tank water to ensure not to kill the beneficial bacteria. Then i'd up the ph to about 7.6 with baking soda and use prime if ammonia or nitrites spike. Hopefully it will recycle and have a fresh start. Sent from my iPhone using Aquarium Advice

Nothing to do with maintenance, I suspect local water supply issues that made the pH drop
A tiny bit of baking soda worked.

 

[Caliban07]

Thanks for the information. Been using very little baking soda and that is helping. The sand gets vacuumed very frequently, water changes 50% or more average once a week or twice. It was a few hours right after a big water change the fish were acting weird and noticed the pH had gone to the lowest of my scale around 6.0, same with another tank I serviced, checked the tap water and had a lower pH than usual, around 6.8 when it has always been 8.0
I'm thinking something in the water supply? But it's been that way now for a few days.

Phone them up and ask why this has happened.

Possible rainfall?


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[gilpi]

Phone them up and ask why this has happened. Possible rainfall? Sent from my iPhone using Aquarium Advice

Good idea, I'll call today. The report on their website was not helpful

 

[gilpi]

Phone them up and ask why this has happened. Possible rainfall? Sent from my iPhone using Aquarium Advice

Called the water company... Very helpful but nothing to report. They'll research a bit more and send me a report.
I'm done with this, moving forward...

 

[gilpi]

So the water company called me back to assure me there were no issues with the water last week after checking their records.
Leaves me to wonder what can make a pH drop that much right after a water change, my mistake or something in the water?
I did both tanks as usual, hosed the water out, treat the tanks with prime and hosed the water in.
According to their readings, their water is always on the neutral side and not hard which comes pretty close to my readings, problem is I never bothered to check KH or GH until after the fact.
Lesson learned here.

Thanks for all the help.

 

[PNWaquarist]

So the water company called me back to assure me there were no issues with the water last week after checking their records.
Leaves me to wonder what can make a pH drop that much right after a water change, my mistake or something in the water?

I'd take their comments with a grain of salt. If they made a boo-boo, admitting it might be a legal liability for them.

It sounds like you've been maintaining multiple tanks at that residence for some time and what you've been doing has worked. It's difficult for me to believe that something on your end caused the pH in all of your tanks to drop simultaneously.

Anyway, I'm glad that this ordeal is apparently over. Hopefully your fish are OK.

 

[Caliban07]

I'd take their comments with a grain of salt. If they made a boo-boo, admitting it might be a legal liability for them.



It sounds like you've been maintaining multiple tanks at that residence for some time and what you've been doing has worked. It's difficult for me to believe that something on your end caused the pH in all of your tanks to drop simultaneously.



Anyway, I'm glad that this ordeal is apparently over. Hopefully your fish are OK.

+1..happy fish keeping again


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[gilpi]

Not to keep dwelling on it but this just made me more aware and a little less trusting with the water I put in my tanks even though the tap is the only source of water I have.
I also blame myself for being over confident since it has worked for so many years and not even having the proper test kit to occasionally check.
On to the next topic
Thanks guys for the support and help.

 

[Delapool]

I have had that as well where I have asked about the water changing and been told nothing has changed their end.

I've got a few test kits and a digital ph meter so have been pretty confident on the results (the first time I got my water checked at the lfs as well).

 

[gilpi]

I have had that as well where I have asked about the water changing and been told nothing has changed their end.

I've got a few test kits and a digital ph meter so have been pretty confident on the results (the first time I got my water checked at the lfs as well).

What was the problem in your particular case and how did you correct it?


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[Delapool]

I had the tap water kh halve when summer started. It's done it twice now over two years.

It's pretty soft water already so I think the tank ph got to 6.7 before I realised.

I've also asked them about salt levels in the water as it seemed high for our suburb. The water report is roughly by suburbs but it is only an annual report. I didn't get much except nothing has changed and the report is what it is. But the section on water treatment said different methods are used so they can't precisely say how the water is treated for each suburb. That to me (perhaps cynical) suggested the water was changing as well if different treatment methods can be used over time.

I picked up some kh buffer as well as adding sea shells off the beach. Just enough to tweak kh between weekly water changes. Also increased water change volume. However (and this is odd) I've concluded that this somehow leads to stem plants browning/rotting at the base and leaves falling off plants. It could all be my imagination so a few months back I added something like 4 times the kh buffer. Doing that was actually at about the recommended dosing on the box as I had been just adding enough to tweak kh before.

Lost all the plants over a few weeks. I've stopped adding the buffer to see if any improvement. I should mention I struggle to grow algae in my tank so plants could well have been on the edge of survival anyways. Every post I've seen suggested my plants should of been fine so could be I'm just hopeless at plant growing in main tank.

 

[PNWaquarist]

Some plants do not respond well to sudden changes in water chemistry. Crypts are famous for this. Four of my Crypt wendtii defoliated after treating my tank with antibiotics last week. Thankfully, they'll eventually come back.

 

[enrgizerbunny]

Lost all the plants over a few weeks. I've stopped adding the buffer to see if any improvement. I should mention I struggle to grow algae in my tank so plants could well have been on the edge of survival anyways. Every post I've seen suggested my plants should of been fine so could be I'm just hopeless at plant growing in main tank.]

Lighting upgrade! Shop lights from Wal-Mart are $10 and they come with a 2 year warranty. Need to warranty mine, actually, but the 3 day blackout should help my BBA problem.

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[Delapool]

Lighting upgrade! Shop lights from Wal-Mart are $10 and they come with a 2 year warranty. Need to warranty mine, actually, but the 3 day blackout should help my BBA problem.

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Could be so, I've just added a hydroponics grow light over the top which gets more red light down at depth. Plants at back may be doing better. Plants at front I think need DIY substrate tabs as I had been doing lots of gravel vacs there before. Idk, small tank grows potted and floating plants fine; large tank - blah! At least the dry ferts seemed to have solved some issues so maybe I'm learning.