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Last night I was doing some reading at the Seachem site in the articles and FAQ's. I read about how during the day as the plants use CO2 during photosynthesis the pH in the tank gradually goes up and at night as the plants and fish create CO2 the pH gradually go down. Being of scientific mind and not sound body I had to test this, I tested the 10g just before lights on then again just after lights out today. The shift was there, it wasn't more than 1 degree pH but it was enough to say aha! I was wondering if anyone using CO2 has tested this or if they would be willing to test this and post the result. I am wanting to know what effect CO2 injection has on this shift. If it makes it go lower at night but keeps it from bouncing up too much during the day, or if it holds steady through night and day. This is purely scientific curiosity and interest, plus something I would like to know before taking the next step and getting a modest CO2 unit. Actual pH readings are great, or even just a general it dropped by so many degrees or whatever.
As well I realize a lightly stocked tank would have different readings from a fully or overstocked tank. I am really just trying to get a general idea of what the swing will be like. I didn't even realize there was a swing now before CO2, so I'm covering my basis here.
Thanks in advance to anyone willing to do this!/:'

"If you're afraid you'll make a mistake, you won't make anything."
-Family Circus

Hi,
The same thing happens in my tank as well. The amount of
pH shift depends upon the KH of the tank. The higher the
KH, the greater the buffering ability of the water and the
smaller the shift.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Thanks Frank,
Ok so now I will not throw out the KH booster just yet, until I know what the shift in my tank will be.

"If you're afraid you'll make a mistake, you won't make anything."
-Family Circus

The shift is always there. How much depends on the amount of co2 injected, amount of plants, if the gas is running 24/7 or not. If gas is running at night the pH will drop further , if the gas is off it may rise a little.

These shifts also occur during the day. We had gas maybe a couple hours before lights on, the pH drops then the plants kick in and start using the co2 and the pH rises again.

My own is Co2 is only on with the lights. I've never really measured it precisely but the shift is about .2-.3 thoughout the day.

The shift is quite natural and will occur anywhere there is plant life, even on non co2 tanks, as the plants swing from consuming Co2 to producing Co2. This swing doesn't effect the fish at all as it's small and gradual. Not something to worry about or try to prevent.

If your KH is 3 or above that's plenty of buffer. Higher KH is a lot more problematic then lower. The more KH the harder for the Co2 to dissolve. Plants are more senstive to high KH then high GH. Certain algaes seem to do better at high KH, maybe because they are better at scrounging the carbonate then plants. Not something to mess with unless there's a very good reason.

---

Some days you're the pigeon and some days you're the statue.

Remember that age and treachery will always triumph over youth and ability.

luvmykrib,

I am completly with Bensaf here (what else is new ). As he said, these swings are normal to aquaria, and they are normal to certain natural water systems as well.

I would assume that mine fluctuates maybe by 0.2, from 6.6 to 6.8. My tab is 7 and if I do my water change in the afternoon I for sure create an instant ph difference of at least 0.2. No problems have been observed though.

I also remember the time when I set up the 125G and didn't quite know yet how to adjust the CO2 right. During these few weeks I had a ph ranging from 7 to 6.5, all within one day. And again, no problems either.

End of story time

I hope this helps,

Ingo

---

Proud Member of the New Jersey Aquatic Gardeners Club

If you want to grow plants, CO2 fertilization is a good idea.

Plants don't care about pH/KH individually, they care about CO2 content.

If you want to decrease the pH, use CO2.
KH is just a gauge along with pH to estimate the CO2 in ppm.

Plants use CO2, not pH.
If there is no CO2, or not enough relative to the light intensity, then the plants, at least some species, will use the KH(-HCO3).

But all plants prefer CO2....

If you add iron, or other fertilizers to increase health and growth, you should defintiely add CO2.

It should be the first on the list for improving plant growth.

It's a nutrient, about 40+% of plants dry weight, the next nutrient, Nitrogen is a mere 1.5%, iron is something like 0.006%.

Which do you think would have the most dramatic effect if all of these was limiting it the tank?
CO2.....

Regards,
Tom Barr

Thanks for your replies everyone, and wow, Tom Barr responded to my post as well, I'm blessed.
I will be adding the CO2 very soon and wanted to know in advance what sorts of things to expect. I am also hoping to increase the light as well. The KH from the tap is quite high but I've finally got the peat figured out so that it is working, it just needed more time to lower KH and GH to a better level. So, the KH (80 ppm)being lower will help the plants use the CO2 better, the lower GH (150 ppm finally)will not really affect anything right? So I'm not too worried about that, and the CO2 will bring the pH down naturally, so no more adjustments to it (unless desperately needed) right? I think I may have this figured out now. I do add iron, potassium, excel, I have been trying to get straight Flourish and Trace as well, although I think the water change brings in a fair bit of minerals already. Anything I'm missing here? I have a product called Plant-Gro N,P,K that is recommended for CO2 injected tanks, but my Nitrate has been high enough I haven't needed it yet. I add the K separately, I am not sure about the P though, I need to test for it. Here's hoping this all works, if I'm back in a panic then please forgive me, I am still relatively new at this, the tank will be 1 yr old this month!

"If you're afraid you'll make a mistake, you won't make anything."
-Family Circus