What causes pH to drop?

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peaches

Feeder Fish
MFK Member
Apr 13, 2005
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Hi! It's been a long time since I've posted here.
I was hoping somebody could give me a few hints as to why the pH of a tank would drop suddenly over a day? It's happened to me with one of my aquariums but I did a small water change and it seemed to help it. But now one of my friends has a tank where the pH has dropped from a consistant 7.0 to 6.0 it actually happened right after they added some aquarium salt. They also lost a few fish. He said he didn't do anything different to the tank at all and he does 25% water changes every three days, he keeps small little fish also. The original fish are doing fine in the tank but does anybody have any idea why or how could this happen? Maybe something I haven't though of?

Also, I've noticed a lot of fishkeepers using Black Lava Rock for their cichlid tanks. My question about that is, where do you normally get black lava rock? From garden centers ect...? And I've also heard of black lava rock being sold for barbecues is that right? If the rocks appear shiny or metallic are they still safe to use in the tank?

I'm sorry for all the questions, but thank you in advance for any help! ;)
 
Many things can cause pH to drop, but a sudden drop from 7.0-6.0 there are fewer things. CO2 is one cause, low buffer capacity, or excessive amounts of detritus buildup.
 
Need to have more info to make a determination. Definately a low buffering capacity. Ph drops when there is a high acid content and the water does not have enough alkilinity (buffering capacity is the abilty of water to neutralize acids )in it to buffer it from the acid. Thats why the ph drops.
 
CO2 is one cause, low buffer capacity, or excessive amounts of detritus buildup
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But with my friends case, wouldn't 25% water changes every three days be enough to keep it under control?

That's why I find this so baffling!

Unless he needs to do larger water changes at a time. Maybe 25% it isn't enough.

Thank you for the replies!
 
Water changes will have nothing to do with this. If the water source has little to no buffering capacity, waterchanges will do nothing. The addition of co2 will cause a dramatic drop quite easily. Detritus build up is not affected by waterchanges. Only gravel washes, and regular filter maintenance will keep detritus from building up.
 
What do you guys use as a buffer?

I use coral. Seems to work quite well.
 
Well, I am just soooo baffled!

This is what's been going on with my friend's tank-
I have tested my own water supply and its a PH of 7. Bang on. I have also virtually stripped down my tank, cleaned all wood and plants, and re-filled. Its still at PH6 though within 30mins. Its just too coincidental that the only thing I have done to both tanks is to add the salt which has then altered both tanks PH values and killed fish in both tanks that had just been added after the salt but non from before adding it
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Anybody know what's the deal here?? :screwy:
 
if i understand correctly a ph of 7 is way low comming out of the tap. tap ph should be at least 7.5. that tells me most buffering capacity is gone. plants, wood, unvaccumed gravel, any kind of acid that is in the tank would drop the ph low, quickly. i buffer my water with baking soda (cheap to buy). usually 1/2 TSP per 5 gallons works to keep the ph up around 7.8 until the next water change.
 
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