Co2 Water Parameter Issue

[MrWaxhead]

I need some advice that I can't seem to find a solid answer too. I have been planted and doing quite well via diy co2 for about 6 months now. I was running two 2L bottles to a 29G tank and changing one to a fresh bottle once a week.

Here is my issue my tap water is very soft, kH is about 25ppm or about 1.4 degrees with a pH of 7.2 I slowly raised my ph via baking soda on each water change to about 80 or 4.5 degrees (and have kept it there for the last 5 months). And drove my pH down to about 6.8 via diy for a co2 level of about 21ppm which was doing very well. Being that it was diy it ran 24/7 and my pH was not really going out of whack even at night when my plants were giving off co2 no more then a .1 shift ever.

Here is my delema, I got a pressurised system for my bday on the weekend, and set it up to drive my pH to the 6.8 pH level, I have the co2 on solenoid that is running on the same timer as my lights so it does not drive co2 at night, but now it seems my pH is swinging way to much. After about 2 to 3 hours of running my co2 is at 6.8 and stays there all day long while the lights are on, but at night when my lights are down/no injection my pH is jumping up to 7.4 for a .6 nightly swing by morning , and I am worried about the health of my shrimp and fish with that much of a swing.

Should I rig my co2 onto a seperate timer and let run on a longer cycle (like still pump for co2 for 6 hours after light down etc) untill i find a balance where my pH does not drive back up like that? (would seem to make sense since my diy was not causing my pH to fall much below 6.8 even on lights off) or what ever it takes to hold a steady 6.8 ish range as that is giving me a 21ppm level of co2 and my plants and fish and shrimp seem to do very well at that level, but the nightly drive to 7.4 is scaring me some. I have monitored this for the last two nights and its consistant 6.8 while driving and 7.4 by morning.

Also is that much of of a pH shift normal with my water parameters, IE is it due to a unatural 4.5 degree hardness since its naturally at 1.5 I hope that is not the case as I have cherry reds in my tank and even 6.8 is lower that I would like to give them, I would prefer to go harder water and higher pH in the 7.2 range, but was worried about raising my kH to levels that would merrit that. As I would have to up my kH to 200ppm or 11.2degrees to get my pH to 7.2 for 21ppm co2. And I don't want to piss with what seems to be working, I mainly want to stablize my pH levels again. I am probably going to put my co2 on a longer timer tonight and try but would love some help in the mean time incase I am making a dumb choice. I am just very concerned about my critters hehe. Thanks very much in advance.

 

[plantbrain]

Adding more KH is not going to help you and just makes an added step.
A KH of 1 is fine.

I've questioned the need for KH at all.............but the real issue is to be able to use the pH/Kh relationship to measure CO2.

With no KH, you cannot do it directly.

But the table does well at a KH of 1,2,3,5,10,20 etc.

Regards,
Tom Barr

 

[MrWaxhead]

Well, my issue was more of a pH issue, but I have since solved it by running my co2 on a seperate timer, I have to run my co2 6 hours after lights down, and it starts up 1 hour before lights on and I am now holding a steady 6.8

But on your point maybe I am dead wrong but I though pH and kH were dirrectly tied together. As would I not have to drive my pH down to 6.3 to obtain a co2 level of 21-22 ppm with a kH of 1.4 or 25ppm? And for me that is too acidic for my cherry reds (which I thought liked a alkaline setting, and I am still in the acidic range at 6.8 but much better then 6.3 would be). By upping my kH to 80ppm or 4.5 degrees I have my co2 at 21 ppm with a pH of 6.8 So for me kH makes a huge difference as I don't want to have my pH at 6.3 for the level of co2 that I wanted. If I am wrong please let me know. I also thought a low kH made your water more prone to pH swings and or crashes.

 

[plantbrain]

Fish care about the KH/GH, not the pH.

Think about this.

What happens when you do a large water change?
The tap pH is much different than the tank's pH in a CO2 enriched tank.

When we do large water changes in planted tanks like myself , Amano and many others suggest, does this harm the fish in anyway?

No.

You can do daily 80% water changes to prove this to yourself.
If you change the GH/KH dramatically, that will hurt the fish.

CO2 additions to lower pH are quite different than say adding HCl(this destroys KH also though) with respect to fish health.

Basically, do not worry about it.
I have all sorts of wimpty fragile fish and have never had an issue.

If you want tp play around with different KH/Ph combos that's fine, but it'as not needed.
CO2 does not influence the salt osmosis differences like KH, GH or salinity does.

It's not a salt nor a strong base or acid
It's just an extra step if you want to do it you may, but it does not help the fish nor the plants.
Most fish have no issues with 1.5 KH differences nor a pH change from 6.2 to 6.7

Regards,
Tom Barr

 

[MrWaxhead]

Ahh thank you very much, I was under the impression that cherry reds prefered alkaline parameters and my crs shrimp in another tank preffered slightly acidic. I have been keeping both tanks about 6.8 just for ease as like you said I don't want to piss with levels to much, I was just worried about my cherries in a 6.3 enviroment. I am pretty new to plant keeping but have had tanks for years. So finding a balance has been a challenge and fun at the same time.

So as a question, are you saying the pH swing of 6.8 to 7.4 was not a problem or was my solution of running co2 longer to hold a 6.8 and a decent level of co2 right? thanks in advance