Water woes, CO2, and buffering

[Russ]

I need some help understanding my tap water and what I should be doing to buffer it properly.

H2O comes out of the tap at PH8.2; KH 5; GH11. As my 46g bowfront (100% Flourite) has aged (7 months old) the PH settles lower and lower after a large water change. Now it levels off at 7.3 within 10 minutes. When I then apply CO2 the PH drops very quickly to the target of 6.7 on the PH monitor/controller and will lower a point more after the cO2 stops. If I leave it as is and continue running the CO2 for a couple of days the PH can drop to 6.3 or 6.2 (the CO2 shuts off at 6.7) and stays there, without rebounding. I started running a power filter in addition to a canister to agitate the surface - this helps initially to bring up the PH a little, but after a day or two even that doesn't help to raise the PH which stays around 6.4 with no CO2 running.

A couple of months ago I started using a tablespoon of Seachem Alkaline Buffer after a water change which stabilizes the PH at about 7.0 or 7.1 and raises the KH to 7 or 7.5 and the GH to 13. The CO2 lowers it to 6.8 and shuts off and it rebounds to trigger the CO2 at 7.0.

Most of the plants seem to like it excepting Rotala wallichii which gets dull looking, doesn't grow, and appears to be starting to fall apart. I assume this is due to the increased KH/GH.

I would appreciate any feedback about this scenario, but I have a few specific questions:

1. I would like to avoid raising the KH/GH so I can grow R. wallichii and some other "soft water" plants. Is there another way of stabilizing the PH and stopping the PH crashes which has killed some fish?

2. A LFS suggested putting some crushed coral in the filter, but this will raise the KH/GH too, right?

3. Am I doing something wrong - like using the wrong stuff to raise the buffering capacity of the water?

4. Does what I describe make sense or am I hallucinating or something?

thanks for any help,


Russ

 

[Tom Barr]

Re: Water woes, CO2, and buffering

Tap seems fine, I would not mess with it.

It'd not worry too much about the pH, the CO2 is the real issue, I'd suspect an issue with the pH measurement, the pH probe, check the difference with the lights on vs off also, stray current will influence the readings.

Regards,
Tom Barr

 

[magicmagni]

Re: Water woes, CO2, and buffering

Can't a large amount of dissoved organics cause the PH to Drop too? Maybe the tank needs a good cleaning?

 

[Tom Barr]

Re: Water woes, CO2, and buffering

Yep, but the poster said after a large water change and I'd assume they do this every so often to the point the organics do not build up.
But..it might do some......

Anyway, they do not need to add the more KH, R wallichii prefers softer KH water as do 2-3 plants.

Using the tap water should be fine therefore and do not add more KH.

Regards,
Tom Barr

 

[Russ]

Re: Water woes, CO2, and buffering

Tom,

Taking what you said to heart, I tried shutting off the lights, unplugging everything, etc., and it doesn't seem to make a difference in the PH monitor readings and my test kits (2 used) seem to be in agreement with the monitor. I did clean the probe which dropped the reading by .1.

It does seem that something is causing the PH to drop more than it should on it’s own; maybe the buffering capacity of the water is just not very robust. Is that possible? This may be totally routine and moot, but I looked at the water service's web site and they say the water is well water which is softened with lime and alum and then "recarbonized" with CO2 to "stabilize" it. Mean anything?

This is how the water is acting now. I did a 70% water change and took your advice to not mess with the water by adding anything and things do seem to be better. But the water comes out of the tap at 8.3 (measured w/ PH monitor and 2 test kits) and after the water change the tank water falls immediately to 7.5 (which seems like a lot to me). I set the CO2 monitor/controller to trigger at 6.9 and it shuts off at 6.7. The CO2 goes on and off with the lights and in the morning the PH is at 7.0. This seems OK for the moment, but I'm afraid I'm going to get a repeat of the PH crashes and lose some really nice fish. I guess the once a week 50% water change part of EI will help with that.

Tom, any comments on this? I’m going to start keeping a log of all my readings and ferts.

magicmagni:
I have had that thought, but it's been acting this way pretty much since the beginning and the tank doesn't seem to be especially dirty.


Thanks for considering all this guys,

-Russ

 

[Tom Barr]

Re: Water woes, CO2, and buffering

Russ, if the KH is 5 degrees, you should have no problems at all with the tap.
Some equilibration occurs when you add the tap.
Add enough CO2 gas to drop the pH to 6.6 to 6.7 range, keep it there.
You'll note that's a bit higher than what you now have, adding more surface movement/current will also help a tad.

Test the pH after allowing the tap to set out for 24 hours in a glass etc.
What you observe is normal and nothing to worry about.
You do need to set the pH controller in a more narrow range and add more CO2.

Regards,
Tom Barr

 

[Russ]

Re: Water woes, CO2, and buffering

Thanks, Tom.

-Russ