pH Changes

Roan Art

Roan Art

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Oct 7, 2005
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I've been tracking my aquarium data and have noticed a trend in pH changes.

Before water changes, my pH is 7.4, after a change it's at 7.8. This change can happen over 2 days course. In order to maintain consistancy, in this type of instance, would it be prudent to use chemicals to lower the new water pH to 7.4 instead of waiting for it to "naturally" occur? .4 seems like a large drop to me, but I'm relatively new to the hobby. Is this normal and safe for the fishes? I've rainbows, corycats, ghost shrimp, and a few neon tetras.

If one did lower the pH, would it just lower even further as per the trend?

I have a planted tank with 3 moderate-sized pieces of Malaysian driftwood in my tank, along with some rather large black pearl soapstone -- which I think are also buffering the water somewhat.

Thanks!
Roan
 
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Take some tapwater and test it right away.

Then fill a shallow bowl with the tapwater and leave it overnight, then test it.

Your pH drop may just be CO2 degassing over a couple of days, and this test will validate that statement.
 
happychem said:
Take some tapwater and test it right away.

Then fill a shallow bowl with the tapwater and leave it overnight, then test it.

Your pH drop may just be CO2 degassing over a couple of days, and this test will validate that statement.
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I was just doing that when I saw this post :)

Fresh tap is 7.8, which I expected since I use a python to fill my tanks. I'll post in the morning what the pH is after it sits over night.

Roan
 
If you have fairly high alkalinity (which you may based on your other post), adding aeration to a glass of water overnight may be more effective. But we'll see, this way is simpler, so it's best to try that first.
 
happychem said:
If you have fairly high alkalinity (which you may based on your other post), adding aeration to a glass of water overnight may be more effective. But we'll see, this way is simpler, so it's best to try that first.
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I hope so :) I love rainbows and that's the recommended pH for them. I know fish can adapt, but some of the ones I am looking at buying are wild caught.

I'll post in the early pm tomorrow. I got caught up in something and forgot to put water in a dish :duh:

Roan
 
happychem said:
Take some tapwater and test it right away.

Then fill a shallow bowl with the tapwater and leave it overnight, then test it.

Your pH drop may just be CO2 degassing over a couple of days, and this test will validate that statement.
Click to expand...

Happy Chem, I think you might have this backwards. Adding Co2 lowers ph, outgassing would raise it agian.

I had a similar situation where tap was ph 7.3. After letting the water stand overnight the pH rose to 7.6.
 
tazcrash69 said:
Happy Chem, I think you might have this backwards. Adding Co2 lowers ph, outgassing would raise it agian.

I had a similar situation where tap was ph 7.3. After letting the water stand overnight the pH rose to 7.6.
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Wow, that's interesting. Your's went up and mine goes down :P

I need to test my other tanks over an equal period of time and see if the same thing happens in there. If the tap water is still around 7.8 when I test it tomorrow, I bet a dozen donuts that it has to do with the steatite rocks I have in that big tank. I have real soapstone in two other tanks, and a mix of catlinite, soapstone and steatite in another tank.

We'll see! :P

Roan
 
Yup, had it backwards. I got caught up in the process and wasn't paying close enough attention to which pH was being measured when. It is, however, possible that the CO2 level is increasing with time as well (ingassing, as it were :P). Not as likely, but possible. In any event, this test is always best to do whenever there's a pH anomaly like this.

Testing KH as well will also help figure out what's happening.

2 days is pretty quick for a pH drop, which is why I am thinking CO2 equilibrium, it is late in the year for low CO2 though. I'm assuming that when you say that it lowers over 2 days that it stays at 7.4 afterwards. If it keeps dropping then it could be bioacidification or it's something else in the tank.
 
There is also the side factor that many utilities add short-term buffers to soft water (can you say phosphate-based?) to protect pipes while the water is in the system. As they do when added to fish tanks as "buffers", after 1-3 days the water is back to baseline.

Then if you add the complications of higher dissolved gases at lower temp and higher pressure, I would never try to predict what any given water would be as baseline after aging.

But if you do contact your utility, they are usually quite helpful and will willingly (as they must legally in this country) give you the info on baseline pH and hardness and alkalinity and whether or not they add buffers or "agents" for pipe protection.
 
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happychem said:
Yup, had it backwards. I got caught up in the process and wasn't paying close enough attention to which pH was being measured when. It is, however, possible that the CO2 level is increasing with time as well (ingassing, as it were :P). Not as likely, but possible. In any event, this test is always best to do whenever there's a pH anomaly like this.
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Soon as the kits get here :)

Testing KH as well will also help figure out what's happening.
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KH is 13, I think :) I'll test it again tomorrow cause I may have gone over a bit. It's 11-13, in there.

2 days is pretty quick for a pH drop, which is why I am thinking CO2 equilibrium, it is late in the year for low CO2 though. I'm assuming that when you say that it lowers over 2 days that it stays at 7.4 afterwards.
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Would aquarium salt lower the pH? I've got salt in there that I forgot about, but it's been there since I started monitoring the pH and have been adding at every water change to keep the levels constant. Fighting a fungus on the rainbows. Fungus loves rainbows. Blargh.

If it keeps dropping then it could be bioacidification or it's something else in the tank.
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Blargh, yah lost me :) I'd ask my husband for clarification, but he's deep into a MechWarrior mission :o

So, that said, could you explain what you mean by bioacidification? Is that referring to organic absorption?

Hrm, what about flourite? I've got about 3-4" of that in there -- 3 bags worth.

Roan
 
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