WOW! Co2 pH bounce

Ranger

Ranger

AC Members
Jun 20, 2001
117
2
18
Everett, WA
Hi Everyone,

I am setting up a 75g planted tank. It’s going to be real nice, full on hood and stand, 4wpg, and semi-auto CO2 system. I have it set up and cycling in the garage with few fish, and no plants or substrate for now.
Here’s my questions: I set up my reactor and CO2 and ran it over the week end. The starting Ph was approx 7.6 and of course I was able to drop it to around 6.4 with the CO2. With a kH of around 3.5 this puts me right in the 20-40ppm of CO2…great!…………but when the CO2 turns off at night the pH is back at 7.6 by the next morning. That seems like a huge daily swing to me. Especially considering the scale is logarithmic.
Is that type of fluctuation routine? Does anyone else have that with their CO2 turning off at night?
Do you think the fluctuation will be less once the system has gravel and plants due some biological effects on buffering?
I used DIY CO2 before on my 45g so I didn’t experience that. In fact when I test the pH I can shake the vile and actually watch the color change as the agitation off gases the CO2.
Thanks
 
that kind of a swing is perfectly normal, and since co2 isnt changing the actual buffer of the water, has no ill effect on fish like a low-buffer swing/crash would. you're good to go. :)

also, be careful of overdose.. 30ppm is sufficient for most all plants.. anything more than that and i would think you'd be risking the respiration of your fish.
 
I would highly suggest grabbing a Drop Checker, alot more accurate than a KH reading, and will provide you a visual reading 24/7.
 
Thanks for the feed back J RR,
Thanks Riiz
Already working on the drop checker. Did a DIY one but the metal lid started rusting so I think it polluted the solution. For now I think my Kh reading is good because our tap water here is so soft it doesn’t even register 1 degree on my test kit, so I raised the tank to 3.5 by adding the baking soda. Once I get all the goodies in I’ll want the reliability of the checker.
 
Yeah, my pH swings from 6.4 to 7.4 daily(or nightly, as the case may be). No problem at all.

Generally, pH is of concern due to it's correlation with TDS, where a change in pH reflects a change in TDS and can be harmful to fish.. With co2, you are affecting pH without messing with TDS.
 
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