Question on kH / pH Chart

[Digimon]

Hi,

I have BBA in my tank.

Wanted to get my CO2 level right before going into other areas, but in the process, stumbled on the question below. I could not get my CO2 level right, but it is consistent.

Question :
When using the kH / pH Chart to gauge the CO2 level in the tank, do we need to have a standard tap water’s pH?

Reason I’m asking this is….

Initial setup :
kH = 3, pH = 6.9, CO2 at ~ 2 bubbles/sec.
Slowly increase CO2 to 5-6 bubbles/sec over a few days, but still could not achieve CO2 at 30ppm.
kH = 3, pH = 6.6
- Critters ok
- Plants bubbling madly
Decided to measured tap water, pH = 7.6

Could not increase my CO2 further as the bio balls in my reactor started to jam.
Found that the pH had actually dropped by 1.0 from 7.6 (tap water) to 6.6 (tank with CO2). My friends with similar setup need ~ 2 bubbles/sec to achieve pH = 6.5, with kH = 3. Found their tap water pH = 7.0-7.1 .

Then, 2 months ago, found kH = 3, pH = 6.2 .
- Critters ok
- Plants bubbling madly
Measured tap water, pH = 7.1

Adjusted CO2 to ~2 bubbles/sec to achieve a pH of 6.5 .
Looks like the drop in the tap water’s pH affected my tank’s pH.

As we are using the kH / pH Chart to gauge the CO2 level in the tank, shouldn’t we be looking at the difference in pH before and after CO2 injection?

Assuming kH = 3, to achieve pH = 6.5 (CO2 at 30ppm),
a) from tap water pH = 7.6 to 6.5, need to lower by 1.1 .
b) from tap water pH = 7.1 to 6.5, need to lower by 0.6 .
through CO2 injection.

With a), I need to pump more CO2 to lower the pH by 1.1, thus wouldn’t the tank have more CO2? (assuming no CO2 loss at the dissolving stage).

Can anybody enlighten me on this?

Here are some info on my tank (which I think may be related to pH level, CO2 diffusing / dissolving) :
- 2 feet tank.
- Lapis sand as substrate (0.5” 1st layer, 1 - 2” 3rd layer).
- JBL as base fert (0.5” 2nd layer).
- 1 small drift wood.
- CO2 from pressurized cylinder, with solenoid valve & timer, (fr NA).
- Internal reactor with atomizer & 3 bio balls inside.
(Inlet from filter, outlet to rainbar near tank bottom with holes pointing to other side of tank).
- Eheim External Canister 2026 Pro II Filter, on to highest flowrate.
- kH = 3, achieved using bicarbonate, added during water change.
- pH tested using pH Test pen (Checked / calibrated with Buffer 7.0 before each usage)
- pH measured at few intervals.
- 70% - 80% water change once a week.
- Tank set up since Feb 04.

I really can’t find anything in my tank causing pH to rise.

Hope somebody can advise me on this. Thanks a lot in advance.

[vinz]

Siong ah, reading your post. :P

First of all, you seem to have neglected measuring the KH of the tap water, or at least left it out. If the KH of your tap water is different then that of the tank water, then the difference in pH tells you nothing. Raising KH of water raises its' pH.

You should be doing it this way:

1. Get a sample of water from your tank in a CLEAN container (you don't want any contaminants that might mess with the water's pH and KH. Preferably just before your CO2 system starts injecting (assuming you are using a solenoid).

2. Cover (not with your hand as skin oils, etc could contaminate the sample) and shake vigorously for a few minutes. This is to shake out any CO2. Then open and let the sample sit for a day to allow the remaining CO2 to escape (osmosis) and drop down to ambient levels.

3. Measure the pH of the sample. This will be the real base pH for your comparisons. KH can be neglected here as the sample is from your tank. This will also account for any unknown pH/KH source in your tank.

4. Off the top of my head, you should be trying to get a drop of 1.1 to 1.4 pH from this base pH to attain 20 to 30ppm of CO2 in your tank water. I am not very sure on these numbers. I think PeterGwee or BCLee will know (I'll PM them to look at this thread).

BTW, it's KH (capital K + capital H) not kH. pH (small p + capital H) is correct. I'm fussy this way.

[PeterGwee]

Bclee mentioned 1.5-1.7 drop in pH from ambient level I think from the post last time. The KH need to be above 0 though for it to work. This method is doggy as well if some acid skew the pH for some reason.

Go the normal approach for measuring CO2. Minimize surface movement but strive to have some just in case your plants stop producing O2. Get a better reactor which will give you a fast response time. (I'm still dogged by this until I get my DIY external reactor to work...). As Tom mentioned, a good CO2 system should be able to hit 30ppm of CO2 within an hour or so from ambient CO2 levels (3-4ppm).

I'll post more once I get the response time issue out of the way...



Regards
Peter Gwee

[barmby]

[quote:9de5f8cd47="Digimon"]Hi,

I have BBA in my tank.

Wanted to get my CO2 level right before going into other areas, but in the process, stumbled on the question below. I could not get my CO2 level right, but it is consistent.
[/quote:9de5f8cd47]

Getting CO2 up to 20-30 ppm within 1/2 to 1 hour after lights on till shut off - IS THE SINGLE MOST DIFFICULT THING TO ACHIEVE.

Work on that. You are not alone. Me too having this issue.

[Digimon]

Hi Guys,

Thanks for the advice & encouragement. And thanks for correcting me on the KH, Vinz.

Will give a try on the method of getting a drop from the ambient level.

Initially, I was using a 2 bio balls reactor (shorter one) & filter flow rate was set at medium. Later, changed to a 3 bio balls reactor (longer one), with a atomizer inside. Also increased my filter flow rate to max, plus putting in the rainbar at the bottom. Dissolving rate improved, pH is nearly to my target but still can’t be met. Will try an external reactor when I have the budget.

Currently, I managed to get my pH = 6.5, noticed my tap water’s pH now is 7.1 .

But still unclear on the KH / pH Chart thing.

After water change, measured my tank’s KH, increase from 1 to 3 using Bicarbonate.
Next, try to achieve pH = 6.5 (CO2 at 30ppm),
Tank A : from tap water pH = 7.6 to 6.5, pumped 5 – 6 bubbles/sec of CO2;
Tank B : from tap water pH = 7.1 to 6.5, pumped ~ 2 bubbles/sec of CO2.

Both Tank A and Tank B have the same setup.

Wouldn’t Tank A have more CO2 than Tank B even though both are at pH 6.5 after an hour?

Did I use the chart correctly?

Vinz,
I did not measure the KH from the tap directly. After topping up my tank with tap water, I measured the KH from the tank and found KH = 1. Added Bicarbonate to raise KH to 3. Then adjust my CO2 valve and check with pH Test Pen 1 & 2 hours later (to get pH = 6.5). Did I do wrongly?

[vinz]

[quote:e622fbfc99="PeterGwee"]...

This method is doggy as well if some acid skew the pH for some reason.

...

Regards
Peter Gwee [/quote:e622fbfc99]

But that's exactly the reason for this method, to account for anything else that might skew the pH and make the chart inapplicable.

[PeterGwee]

Oh right....

Regards
Peter Gwee

[vinz]

Digimon,

A fundamental error in your measurements is that you are associating the pH of the tap water with the KH of the tank water.

Forget about measuring the pH or KH of the tap water because once you add it into the tank, both values are affected by the contents of the tank, including the old water.

Correctly, you raise the KH of your tank water before you measure the pH. But, it will take a while for the bicarbonate to be distributed uniformly, and hence the final pH and KH values of the tank water. I would say give it an hour.

If you really get down to it, depending on circulation, CO2 distribution in your tank may not be uniform and pH values can vary. (Now, doesn't that just screw things up a little bit more?) Most ppl ignore this, but PeterGwee doesn't.

If you want to follow the chart strictly, then ignore the start values of your KH and pH. Just aim for KH 3, pH 6.5 and assume the CO2 level is as the chart says it is.

If you want to depend on pH drop from a base value, then you need to go thru the process I described in my earlier post.

As for the comparison between tank A and B... no two tanks are exactly alike. Even if you set them up exactly the same from day one with the same plants, etc, there will be variations... just less. There are many factors that affect it. E.g.
- are the water source the same? (affects chemistry, availablity of trace elements (affects photosynthesis rate))
- are the plants exactly same? (affects CO2 consumption rate)
- are there the same number of plants? (affects CO2 consumption rate)
- are the plants getting the same amount of light (age, quality, brand of lights have to be accounted for. affects photosynthesis and hence CO2 consumption)
- is the evaporation rate the same? (fan speed, water temperature, location, air circulation of the room, humidity - affects CO2 lost rate)
- is water turbulence the same (affects CO2 lost rate)
- any driftwood? (affects chemistry, esp. pH)
- are the driftwood releasing the same amount of tannin? (affects chemistry, esp. pH)

There's more.

Pick one method.

[vinz]

Oh, and given that CO2 distribution may not be uniform, especially in large tanks... are the BBA in your tank growing only in a few areas? Try changing the water circulation... it might help. It did for me.

[PeterGwee]

[quote:50c75e0f89="Digimon"]Hi,

I have BBA in my tank.

Wanted to get my CO2 level right before going into other areas, but in the process, stumbled on the question below. I could not get my CO2 level right, but it is consistent.

Question :
When using the kH / pH Chart to gauge the CO2 level in the tank, do we need to have a standard tap water’s pH?

Reason I’m asking this is….

Initial setup :
kH = 3, pH = 6.9, CO2 at ~ 2 bubbles/sec.
Slowly increase CO2 to 5-6 bubbles/sec over a few days, but still could not achieve CO2 at 30ppm.
kH = 3, pH = 6.6
- Critters ok
- Plants bubbling madly
Decided to measured tap water, pH = 7.6

Could not increase my CO2 further as the bio balls in my reactor started to jam.
Found that the pH had actually dropped by 1.0 from 7.6 (tap water) to 6.6 (tank with CO2). My friends with similar setup need ~ 2 bubbles/sec to achieve pH = 6.5, with kH = 3. Found their tap water pH = 7.0-7.1 .

Then, 2 months ago, found kH = 3, pH = 6.2 .
- Critters ok
- Plants bubbling madly
Measured tap water, pH = 7.1

Adjusted CO2 to ~2 bubbles/sec to achieve a pH of 6.5 .
Looks like the drop in the tap water’s pH affected my tank’s pH.

As we are using the kH / pH Chart to gauge the CO2 level in the tank, shouldn’t we be looking at the difference in pH before and after CO2 injection?

Assuming kH = 3, to achieve pH = 6.5 (CO2 at 30ppm),
a) from tap water pH = 7.6 to 6.5, need to lower by 1.1 .
b) from tap water pH = 7.1 to 6.5, need to lower by 0.6 .
through CO2 injection.

With a), I need to pump more CO2 to lower the pH by 1.1, thus wouldn’t the tank have more CO2? (assuming no CO2 loss at the dissolving stage).

Can anybody enlighten me on this?

Here are some info on my tank (which I think may be related to pH level, CO2 diffusing / dissolving) :
- 2 feet tank.
- Lapis sand as substrate (0.5” 1st layer, 1 - 2” 3rd layer).
- JBL as base fert (0.5” 2nd layer).
- 1 small drift wood.
- CO2 from pressurized cylinder, with solenoid valve & timer, (fr NA).
- Internal reactor with atomizer & 3 bio balls inside.
(Inlet from filter, outlet to rainbar near tank bottom with holes pointing to other side of tank).
- Eheim External Canister 2026 Pro II Filter, on to highest flowrate.
- kH = 3, achieved using bicarbonate, added during water change.
- pH tested using pH Test pen (Checked / calibrated with Buffer 7.0 before each usage)
- pH measured at few intervals.
- 70% - 80% water change once a week.
- Tank set up since Feb 04.

I really can’t find anything in my tank causing pH to rise.

Hope somebody can advise me on this. Thanks a lot in advance.[/quote:50c75e0f89]

Influence from acids seems highly unlikely as you are changing large amount of water out of the tank weekly. Large amount of pearling also indicated that the plants are likely to have enough CO2 and nutrients. All that is basically left is maintenance. Uproot all your stem plants and clean/remove all the infected portions. Clean the filter and do every so often so that slowing down of flow in the tank does not occur. If the gravels are infected, rotate them down to the lower portions. Finally, do a large water change like you usually do and add back the nutrients. Watch the CO2 closely and in doubt consider adding slightly more slowly but remember to watch your critters when you do so.

Digimon, do you have large amount of surface turbulence? Did you check for leaks in your CO2 system? (5-6bps is a lot for a 2ft tank ime....I use about 1 bubble every 3 seconds for my large reactor running with a maxi-jet 900 for my 2ft tank.)

Regards
Peter Gwee

[Digimon]

Vinz,
Every changes I make on the KH (Bicarbonate) or pH (CO2 bubbles/sec), I usually waited a min of 1 hour before I re-take the measurement.

Actually both Tank A & B are the same tank (my 2 feet tank). Was getting the value of KH = 3 & pH = 6.6 with 5 – 6 bubbles/sec 3 months ago on my tank. Then 1 month ago, decided to do a check and found KH = 3, pH = 6.2. Adjusted the CO2 to ~ 2 bubbles/sec to get pH = 6.5.

There were no changes on the setup or re-scaping, except for some weekly pruning here and there during water changes. Do a check on my water source and found the pH dropped from 7.6 to 7.1 . That’s when the question popped into my mind.

But I do agree that there is no 100% similarity at any point of time as bulbs deteriorate, environment changes, etc.

Will give a try on the base value method to verify my CO2 level.

Btw, my BBA are all over the tank. Once I get my CO2 right, will fill up the Beginner’s Info Sheet.


Peter,
The only surface turbulence I have is from the cooling fan (single) on top of the tank blowing at 45 degrees angle. Will step up on my maintenance.


Thanks a lot for your patience and advice, guys.

[Digimon]

[quote:26dcdbb8b9="Vinz"]Digimon,

A fundamental error in your measurements is that you are associating the pH of the tap water with the KH of the tank water.
......[/quote:26dcdbb8b9]

Vinz,
I think I was a bit slow in understanding some of the points brought up. After re-reading the points, found that I did not bring out / highlight properly on the part of the tap water’s pH.

During the early stage of the setup, I was trying to get the setting for the CO2 level in my tank. So after every water change, I’ll test the pH of the water in the tank (without CO2 & lights) after an hour of circulation. pH is normally 7.6 with KH 3. After lights on and CO2 injection for an hour, I’ll test the pH again, found to be 6.8 at 5 – 6 bubbles/sec. After weeks of trying, I do a check on my tap water and found pH = 7.6 +/- 0.1 . Actually when I say tap water’s pH = 7.6, it actually is also the pH of my tank (an hour later) after water change.

Subsequently, I increased my filter flow rate, added rainbar at the bottom of tank, point the flow from behind the tank to the front, changed my reactor to a longer one with atomizer inside and more bio balls. Managed to improve the pH to 6.6 and maintained till 1 month ago, during one of the testing, found pH dropped to 6.2. Found my tap water’s pH also dropped coincidentally.

This is how the story begins.

I’m not trying to challenge anything here. Just wan to make sure I am doing the right thing with the KH / pH chart. Now that there is another method to verify the CO2 level, I’ll give it a shot.

My apologies for missing out some of the details.