Calling all pressurized users! How low have you dropped pH!?

[7Enigma]

Hello everyone,

I very interested in the effects of CO2 on pH. I'm interested in hearing how low you've dropped your pH before in your tanks, and if possible what KH your water is at? I assume most of these experiences will be from accidentally over-injecting (and possibly/probably killing your fish).

I'm trying to find a way to get the pH of the water BELOW 4.0 solely using CO2 as my "acid".

Thanks in advance!

 

[maxwell1295]

I haven't gone below 6.4 or so. I buffer my water with a little baking soda to prevent it from falling any lower. My tap is basically RO water, 6.4 and no hardness to speak of. Without the baking soda I could easily dip down in the 5's. In fact, my pH dropped well below 6.0 just by adding 2 large pieces of driftwood.

 

[7Enigma]

I've hit ~6.0 on DIY when I added too much yeast and the temp in the room was in the upper 80's before so I know we can get much lower than that! Thanks for the reply.

 

[dapellegrini]

Well, I have never taken mine below 6.8, but my system is automated, and wouldn't (normally) allow for such an error. My tap is ~8.0 with ~6dkH.

I have to imagine that maintaining a system below 6.0 would not be healthy for anything, but I am also interested to hear what others may know here.

 

[7Enigma]

This is not to be used with fish. And I'll add the caveat that hopefully someone who took it really low had an accurate way of measuring the pH (such as with a probe).

Tom Barr, you there? I seem to remember reading about some tests you or someone from your site did with really high CO2 levels (in the hundreds). Any pH measurement on that?

Or does anyone have a way to determine the amount of CO2 (ppm) required to drop the pH down to below 4.0? All the charts I've seen are for biological ranges...

 

[frostby]

normal H20 is 8.0, kh 15, been as low as 6.4... but fish were swimming upside down. That didn't last long 8O

 

[7Enigma]

Yeesh, that is pretty high. I wish you had a KH of 2 though....

 

[GlitcH]

My tap water has a PH of 7.7 or so......my tank ranges between 6.4 and 6.9. No injection overnight is the reason for the range.

 

[7Enigma]

OK, I've got a better question. What is the low pH limit of CO2 in water? i.e. does it keep going down with more and more carbonic acid, or does it reach a point where it stops decreasing?

 

[Lonewolfblue]

My kh is 60, and the lowest I've had mine was about 5.8 at one time. I normally like keeping it at 6.2 though.

 

[JRagg]

OK, I've got a better question. What is the low pH limit of CO2 in water? i.e. does it keep going down with more and more carbonic acid, or does it reach a point where it stops decreasing?

I would say that just like any acid (or base for that matter), the acid in its purest form has a pH limit to it. I'm not sure what the pH of pure carbonic acid is, but I'm sure that you could look up a MSDS for it if you wanted to. I'm also pretty sure I've seen a calculator where you can enter the pH and the KH and get a ppm of CO2 spit out. I know there is a direct equation for it. Just enter in low values of pH and see what the ppm of CO2 is.

 

[MSU Fan]

I recently had an unfortunate "tank dump" with my pressurized CO2 - My wife and I noticed the fish swimming eratically and I immediately did all the tests to find out what was wrong.

Nothing too surprising found except for one caveat - my PH registered at 6.0 (lowest on the scale) and my KH was ~5.0. Using Chuck's Planted Aquarium Calculator, that is 150ppm CO2! Since the PH could have been lower than 6, the CO2 levels could have been much worse.I only lost 2 fish (i immediately cut my CO2 and turned on all airstones) through the whole episode.

According to the calculator:
5.8PH@5KH - 238ppm
5.6PH@5KH - 377ppm

BTW, my normal water is 7.0PH and 1-2KH, but with pressurized my water is ~6.2 & 1-2KH

 

[majolo]

According to Wikipedia on carbonic acid:

For normal atmospherics conditions ... we get a slightly acid solution (pH = 5.7) and the dissolved carbon is now essentially in the CO2 form.

Apparently in order to get a pH below 4 from pure carbonic acid, you need about 1 atmosphere of CO2 partial pressure above the solution.

 

[Zezmo]

My Ro/Di water starts at a Ph of 6.0 before CO2 is added. Perhaps start there (RO/DI or Distilled) and then use the CO2 to further drop the Ph.

They make Ph tests that test all the way down. I have a strip (for industrial use) that covers Ph of 1.0 to 9.0 in 1.0 increments. It has like 6 squares of "test" solution on it. Each covers a different range.

 

[malkore]

My dKh is 10 and I've gotten pH down to 6.2 in my 75gallon a couple times after refilling teh CO2 and doinking around with the bubble rate.

 

[IceH2O]

I don't inject but my pH is below 6. It doesn't even register on my AP test. My KH is 0, guess that isn't possible but its not 1, it might be .1 lol. It comes out of my well like this, nothing added or removed.

I don't seem to be having any problems with my fish and the plants are doing well. Wish I could tell you how low it is but I don't have or know of anyone with a pH probe.

 

[Wizzard~Of~Ozz]

Well, take a reading of tonic water or such, pretty sure it will be around 4.5 and that would be saturation (this number also comes up in lot of articles regarding Co2 and water)