Why Is The Ph In My Tank Different Than My Tap Water?

Hello, just curious because the only product I use is Seachem Prime and it doesn't affect pH. I used my API test kit and tested my tank water which reads around 7 pH (this is several days after adding Seachem Prime so my readings would not be skewed) and my tap is around 9 pH. I have read keeping a steady pH matters more than the actual value. Due to my findings, each time I do a water change, I am "changing" the pH in my tank. My fish are fine but still curious. I can't really get a reading on the tank after a water change because I ALWAYS add Seachem Prime. My tap water has ammonia in it so... I do large water changes 40-50% every 7-10 days if it matters. Any thoughts? Thanks

 

Do you let your tap water off gass before testing it? It could just be an artificial ph.

 

it is oxygen or CO2 in your supply water .
It has no effect on your fish eitherway .
Excess oxygen in your tap will result in a higher pH out of the tap and extra CO2 out of your tap will result in a lower pH out of tap .
Since they are both gases and actually can not change the physical Hardness of water it matters not at all.

 

Do you let your tap water off gass before testing it? It could just be an artificial ph.

No, since I add it to my tank straight from the tap I did not test it that way

 

Hello, just curious because the only product I use is Seachem Prime and it doesn't affect pH. I used my API test kit and tested my tank water which reads around 7 pH (this is several days after adding Seachem Prime so my readings would not be skewed) and my tap is around 9 pH. I have read keeping a steady pH matters more than the actual value. Due to my findings, each time I do a water change, I am "changing" the pH in my tank. My fish are fine but still curious. I can't really get a reading on the tank after a water change because I ALWAYS add Seachem Prime. My tap water has ammonia in it so... I do large water changes 40-50% every 7-10 days if it matters. Any thoughts? Thanks

Water treatment plants treat domestic (residential, public) water with buffers if the source water (reclaimed, ground, RO, desalinated, surface) has a low pH. Low pH in water causes corrosion of pipes and joint solder. They typically treat the pH with calcium carbonate, lime, soda ash or sodium hydroxide. Once that water leaves the buffering source and is just sitting in air, it slowly returns to it's pretreatment pH (somewhere between 12 to 72 hours later.
You can stabilize your pH to somewhere between your 7 and 9 so that the change is not so rapid and unstable by adding lime chips or crushed coral (my choice) to either your filter overflow (1 cup per 30 gallons tank water-in a mesh bag) or as part of your substrate (1pound per 10 gallons tank water volume).

 

My ph is 6.8 out of the tap. My tanks stabile ph is 6.6. If you leave a bowl of tap water out over night and then test it you get your true ph. As stated above this gives the water a chance to evaporate some of the additives that come from the plant.

 

I think the only time pH will adjust when water is left to "air" is when CO2 comes into play. But other ways of hiking up pH would need an opposing buffer (such as the acids present in a tank) to bring the pH down. I do not think these changes evaporate, but that us just my understanding of things.

 

I think the only time pH will adjust when water is left to "air" is when CO2 comes into play. But other ways of hiking up pH would need an opposing buffer (such as the acids present in a tank) to bring the pH down. I do not think these changes evaporate, but that us just my understanding of things.

pH is simply the measure of hydrogen ions in water. Water that is allowed to 'sit' especially with some surface aggitation, will absorb CO2 and Oxygen from atmospheric air. The same way the ocean absorbs TONS of CO2 from our atmosphere every day. As water does this, it becomes more acidic. When you receive water from a source that has temporarily buffered water that is acidic to start with then sends it to your home, that water is no longer in the presence of a buffer and again will absorb CO2 and the pH will begin to drop. By adding a buffer (calcium carbonate) to your tank, you stabilize your pH by countering this acidification of water by continuously buffering it.

 

pH is simply the measure of hydrogen ions in water. Water that is allowed to 'sit' especially with some surface aggitation, will absorb CO2 and Oxygen from atmospheric air. The same way the ocean absorbs TONS of CO2 from our atmosphere every day. As water does this, it becomes more acidic. When you receive water from a source that has temporarily buffered water that is acidic to start with then sends it to your home, that water is no longer in the presence of a buffer and again will absorb CO2 and the pH will begin to drop. By adding a buffer (calcium carbonate) to your tank, you stabilize your pH by countering this acidification of water by continuously buffering it.

Yes but the amount of hydrogen is not solely dependant on CO2. Therefore just because hydrogen is decreased (to increase pH) does not mean CO2 has been added (that would decrease pH) so gassing off CO2 will only adjust hydrogen ions so much. They aren't adding CO2 to the water, just something that adjusts hydrogen ions downwards.

Edit: to increase pH, hydrogen ions are decreased while hydroxide ions are increased. After reading what I've written, I can see it being about as clear as mud. I can explain it better if I need to.

 

Yes but the amount of hydrogen is not solely dependant on CO2. Therefore just because hydrogen is decreased (to increase pH) does not mean CO2 has been added (that would decrease pH) so gassing off CO2 will only adjust hydrogen ions so much. They aren't adding CO2 to the water, just something that adjusts hydrogen ions downwards.

Edit: to increase pH, hydrogen ions are decreased while hydroxide ions are increased. After reading what I've written, I can see it being about as clear as mud. I can explain it better if I need to.

Exactly, "This is because the carbon dioxide in the air reacts with water to produce carbonic acid. The hydrogen ion (H +) released by carbonic acid ionization decreases the pH of the water."

 

They typically treat the pH with calcium carbonate, lime, soda ash or sodium hydroxide. Once that water leaves the buffering source and is just sitting in air, it slowly returns to it's pretreatment pH (somewhere between 12 to 72 hours later.

I was only responding to this, and trying to explain that if water was treated with something like sodium hydroxide, that the pH may not change during an aging process to pre treatment levels, because the pH change wouldn't in this case, be caused by CO2. I wasn't trying to say that a CO2 gas exchange wouldn't affect pH. I wasn't trying to argue. And I apologize for any confusion this might have caused.