Ph Keeps Raising, What's Going On?

[ObsidianMan]

I've been having a problem with my tank recently.  The Ph keeps increasing.  My water from tap is 7.4 - I put this in the tank, and over the course of a few days it raises to 8.2, and will probably keep increasing...however I do a water change at this point.
 
Water stats:
 
Ammonia: 0.0
Nirite: 0.0
Nitrate: 40
pH: 8.2
 
I have 6 neons and 5 danios in the tank.  There are two ornaments and a few fake plants.
 
Filter is a Fuval 405 - which is very powerful for the tank.  I wondering if the speed of the water could be causing the pH increases?
 
 

 

[fluttermoth]

Flow from your filter won't affect pH.
 
When you're testing the tap water, are you leaving it to stand for 24 hours first? Many water companies temporarily raise or lower pH (to prevent corrosion in the system) and you must let that wear off before you get a true reading.
 
It could be something in your tank that's raising the pH; substrate is the usual culprit. To test that, leave out two identical jars or cups, one with just water, and the other with water and a handful of your substrate. Test them both after a day or two and see if they differ.
 
In any case, pH is far, far less important for fish than hardness, so that's what you want to be concentrating on.

 

[ObsidianMan]

Flow from your filter won't affect pH.
 
When you're testing the tap water, are you leaving it to stand for 24 hours first? Many water companies temporarily raise or lower pH (to prevent corrosion in the system) and you must let that wear off before you get a true reading.
 
It could be something in your tank that's raising the pH; substrate is the usual culprit. To test that, leave out two identical jars or cups, one with just water, and the other with water and a handful of your substrate. Test them both after a day or two and see if they differ.
 
In any case, pH is far, far less important for fish than hardness, so that's what you want to be concentrating on.

 
 
Thanks I will give this a try.
 
I have another 60L downstairs, the pH in this tank is 7.6.  It has the same substrate and ornaments from the same brand, it also has fake planets - though of a different brand.  Pretty much everything in each tank is the same.  Except the water in the 60L upstairs changes to 8.2pH within 48hrs or so.
 
EDIT:  Just wanted to add that waterflow affects the level of oxygenation in the water, which in turn can affect pH.  I'm turning the flow down to 50% in the meantime to see if this has any effect.

 

[fm1978]

As Fluttermoth says, it's likely that additives to the water in your tap are dispersing after a time that then increase the pH. CO2 is sometimes put into water making it more acidic which then gasses off leaving  more basic water left over.

 

[ObsidianMan]

As Fluttermoth says, it's likely that additives to the water in your tap are dispersing after a time that then increase the pH. CO2 is sometimes put into water making it more acidic which then gasses off leaving  more basic water left over.

 
Thanks, but that doesn't explain why the 2nd tank has a completely different pH.

 

[wrightt3]

Oxygenation has no effect at all on the pH. CO2 on the other hand does have an effect. If you use CO2 in your downstairs tank then this may explain the lower pH. High waste content can also lower the pH. It is possible that either of these factors is preventing the pH increasing like it is in your upstairs tank.

 

[ObsidianMan]

Oxygenation has no effect at all on the pH. CO2 on the other hand does have an effect. If you use CO2 in your downstairs tank then this may explain the lower pH. High waste content can also lower the pH. It is possible that either of these factors is preventing the pH increasing like it is in your upstairs tank.

 
Ok thanks.
 
I said 'oxygenation' but I mean aeration.  It was my understanding that aeration causes out-gassing of carbon dioxide...and as carbon leaves the water - there is an increase in pH (there are a good number of sources that confirm this.  It's the opposite effect of adding CO2).  At any rate, if that is not the issue then something else maybe going on.  I'm reluctant to say that this is a natural change in pH, as if I leave the tank the pH continues to increase - it has reached 8.4 previously and I do not want it going higher than that.  So I'm keen to find out what is going on.

 

[wrightt3]

Hmm... that's quite interesting actually, I've never heard of that before. Either way, I can't see as it would have an effect to the same degree as what you are experiencing. The only thing that I could suggest is removing all of the ornaments to see if there is any change. If it stops increasing after removing them, then you can add them back in one by one until you determine which one is causing it.
 
You don't use any crushed coral in you're tank do you? Crushed coral substrate can drastically increase the pH.

 

[ObsidianMan]

Hmm... that's quite interesting actually, I've never heard of that before. Either way, I can't see as it would have an effect to the same degree as what you are experiencing. The only thing that I could suggest is removing all of the ornaments to see if there is any change. If it stops increasing after removing them, then you can add them back in one by one until you determine which one is causing it.
 
You don't use any crushed coral in you're tank do you? Crushed coral substrate can drastically increase the pH.

 
 
No corel.  Just black stone which has always been in all my tanks - and is also in the other tanks.  I will try removing the ornaments.
 
Regarding the aeration and CO2:
 
http/www.troublefreepool.com/threads/28515-Aeration-to-raise-PH?p=240310&viewfull=1#post240310
 
&
 
http/www.asmr.us/Publications/Conference%20Proceedings/2007/0373-Kirby-PA.pdf