Natural pH alterations

[Duncan Dumbreck]

Hi all

So I have been experimenting with various ways of reducing pH naturally. I have been using RO water, and putting various things in it. The obvious ones are oak leaves and peat, but by way of an experiment I put some wood chips in some. It had a far greater effect than anything else. acheiving a pH of around 4.2!!! (oak leaves got to 4.8.)

My question is, would there be anything wrong with using wood chips in place of peat/oak leaves? Might there be other chemicals in them which makes it a bad idea?

Also which of the above methods produce the most stable pH?

 

[dw1305]

Hi all,

My question is, would there be anything wrong with using wood chips in place of peat/oak leaves? Might there be other chemicals in them which makes it a bad idea?

There will be other compounds, if the chips are coniferous they will reduce the pH, but they will toxic contain secondary metabolites like terpenoids, phenols etc. If they are bark chips, (either Oak and conifer bark)
they typically have a pH around pH4, a very high C:N ratio, a lot of lignin and very low levels of
plant nutrients. Again conifer bark isn't suitable, because of the resinous secondary metabolites, but Oak bark is OK. Sphagnum peat differs from the other items mentioned as it has a high CEC, as well as containing humic compounds.

Also which of the above methods produce the most stable pH?

You can't really have a stable pH in very soft water, as you get towards pure H2O (like RO) pH becomes less and less relevant as a parameter.

Have a look a this thread <http://www.apistogramma.com/forum/index.php?threads/another-peat-filtration-question.11247/>.

cheers Darrel

 

[Duncan Dumbreck]

The thread you posted is a definite winner, i can sort of wrap my head around pH sometimes but then my RO water goes and measures 8.9 and so I get very confused. 24 hours later it is down to 7.5, TDS has remained the same? Think it is probably down to the poor quality of my pH meter, and the instability of the soft water.

Hadn't thought about terps, and what wood the chips are. (we have a wood chip boiler) pretty sure it'll be a mixture so I won't be using that batch of water.

 

[gerald]

Even the good meters have a hard time measuring pH in very low conductivity water. When there's so few ions present, a tiny shift in real numbers of ions creates an apparent BIG shift in pH. The meter itself leaches out KCl and affects the reading as you're measuring it. (That's why you keep stirring). The "ISFET" meters are supposed to work a little better than typical glass electrodes in very low conductivity water, but all electric meters have limitations. To be honest, a color dye test kit is probably more useful for aquarists when trying to measure pH at conductivity less than 50 uS. Or you can take Darrel's advice and avoid worry by not measuring pH if your water is that low in ions.

 

[viejo]

Can anyone recommend a source for a good pH indicator solution for the lower ranges? I'm pretty well fed up with meters at any rate.

 

[regani]

You can add sodium chloride or better potassium chloride (because the sodium chloride can contain carbonates as impurity) to the water before you measure pH as they won't affect the pH value but make it easier for the probe to give a correct reading. Indicator solutions will have other types of problems in low conductivity water as all indicators are weak acids or bases themselves. this is usually not a problem if there is plenty of other stuff around affecting the pH but in increasingly pure water the effect of the indicators themselves will start to distort the results.

Also, caring for you pH electrode correctly is quite important to get accurate measurement. A while ago I posted the following on another forum, which may help to get better value out of your pH meter:

..... Ummm, too many words, it won't let me post it.... I'll see if I can get it up as a new topic......

 

[dw1305]

Hi all,

You can add sodium chloride or better potassium chloride (because the sodium chloride can contain carbonates as impurity) to the water before you measure pH as they won't affect the pH value but make it easier for the probe to give a correct reading. Indicator solutions will have other types of problems in low conductivity water as all indicators are weak acids or bases themselves. this is usually not a problem if there is plenty of other stuff around affecting the pH but in increasingly pure water the effect of the indicators themselves will start to distort the results.

That is a great answer, I wish I'd written it. We do have a thread on using a neutral salt to stabilise pH readings, it is this one: <http://www.apistogramma.com/forum/index.php?threads/ok.12048/> and well worth a read.

cheers Darrel

 

[Duncan Dumbreck]

So I just went back having read regani's new thread on pH meters and calibrating I went back to my old faithful chemical test kit, and found exactly what I thought I would. It's quite far wrong for most tanks. I think I may go back to the chemical tests for a while until I can calibrate the meter properly. (Not surprised that it is out of whack having read the thread, my sister borrowed it and I found it drying out without even having the cap put back on it.)

 

[gerald]

Thanks regani -- looks like I was wrong about the KCl leaching from the pH probe affecting the reading. I didnt know you could add KCl to the sample without changing its pH. Also I didn't realize that indicator dyes can change the pH of the sample. What indicator dye do you recommend for measuring in the 4.5 to 6.0 range (below the bromothymol blue range)?

You can add sodium chloride or better potassium chloride (because the sodium chloride can contain carbonates as impurity) to the water before you measure pH as they won't affect the pH value but make it easier for the probe to give a correct reading. Indicator solutions will have other types of problems in low conductivity water as all indicators are weak acids or bases themselves. this is usually not a problem if there is plenty of other stuff around affecting the pH but in increasingly pure water the effect of the indicators themselves will start to distort the results.

Also, caring for you pH electrode correctly is quite important to get accurate measurement. A while ago I posted the following on another forum, which may help to get better value out of your pH meter: .... Ummm, too many words, it won't let me post it.... I'll see if I can get it up as a new topic......

 

[viejo]

Thanks regani -- looks like I was wrong about the KCl leaching from the pH probe affecting the reading. I didnt know you could add KCl to the sample without changing its pH. Also I didn't realize that indicator dyes can change the pH of the sample. What indicator dye do you recommend for measuring in the 4.5 to 6.0 range (below the bromothymol blue range)?

This is pretty much a restatement of my post above. What indicator would you recommend for this range?

 

[regani]

I am not too sure what is out there in terms of commercial indicator mixes in the hobby to cover the lower pH range. You will need a mix to get colour changes for different pH values (same as for your standard indicator solutions available in the hobby). A single indicator like bromothymol blue will just tell you if the pH is above or below a certain value.
Bromo thymol blue is an indicator that actually changes slowly over a wider range, so you get to see yellow below pH 6, blue above pH 7.5 and green (the mixing of yellow and blue) in between.
There are some pH indicator sticks that have a low pH range, but those are usually only available through specialist suppliers for scientific laboratories.
There may be some low pH indicator brands available in the US or Europe, I haven't seen any here Australia. I use a pH pen if I want to check my pH

 

[Duncan Dumbreck]

So just to triple check... I should be able to add pure RO water to my tank with no ill effects, despite the lack of buffering ability as the pH won't matter due to low numbers of ions present?

I've got a TDS meter but have just ordered a conductivity meter ( I know they are basically the same but seeing as you lot seem to all talk in microsiemens it seems to make sense to me to be talking the same language without having to do maths every time.)

I hated chemistry at school, and now I have a reason to want to know I can't get enough of all this learning. Maybe fish tanks should be used to teach science. Nitrogen cycle, pH, acids, bases, buffering, sexual reproduction. The list of potential goes on.

 

[regani]

In principle RO water will not affect the pH of your tank. If you do large water changes with RO water the pH may change a bit, due to the fact that your are diluting any acidic (or basic) stuff present in the tank. But as you rightly pointed out the closer you get to pure water, the less meaningful a value such as pH actually becomes.

 

[dw1305]

Hi all,

What indicator would you recommend for this range?

The low range pH indicator is "Methyl red", a chlorinated hydrocarbon with 2 benzene rings, and I wouldn't particularly want long exposure to it, although it is a powder (I just went and checked the bottle).

Methyl red is a pH indicator; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between...

I've got a TDS meter but have just ordered a conductivity meter ( I know they are basically the same but seeing as you lot seem to all talk in microsiemens it seems to make sense to me to be talking the same language without having to do maths every time.)

It doesn't hurt to have 2 meters, but the maths is pretty straight forward, for most meters the conversion factor is 100 microS = 64ppm TDS, so 100ppm TDS = 156 microS. It will say somewhere what conversion factor the TDS meters uses.

So just to triple check... I should be able to add pure RO water to my tank with no ill effects, despite the lack of buffering ability as the pH won't matter due to low numbers of ions present?

Pretty much, personally I'd either make sure that I have plenty of DOC (dissolved organic carbon) in the tanks water, (from bark, alder cones, Indian Almond leaves etc.) or I'd peat filter the RO first.

Maybe fish tanks should be used to teach science.

We use ours a bit (they are in the teaching lab.)

and there are a couple of Primary School Teachers on UKAPS who have tanks in their classes.

If you want a book and a web link for some relevant chemistry, Diana Walstad's book "Ecology of the Planted Aquarium" <http://www.amazon.co.uk/Ecology-Planted-Aquarium-Diana-Walstad/dp/0967377366> is a really useful resource and the web pages I'd recommend are the "Skeptical Aquarist" <http://www.skepticalaquarist.com/nitrogen-cycle>.

Cheers Darrel

 

[Mike Wise]

I remember back in the stone age when Tetra made a 'pH I' liquid indicator that went down to pH 4.8. I still have the color wheel somewhere. There are times I wish they still made it.

 

[dw1305]

Hi all,

I remember back in the stone age when Tetra made a 'pH I' liquid indicator that went down to pH 4.8. I still have the color wheel somewhere. There are times I wish they still made it.

Mike I think it may be health and safety considerations, most/all? the low range pH indicators (Bromophenol Blue, Methyl Yellow, Congo Red etc) are aromatic compounds, and you don't find many old organic chemists.

You can get low range pH indicator strips for labs etc. These are from Camlab, but I'm sure you could get similar in the US. <http://www.camlab.co.uk/camlab-ph-indicator-strips-p25677.aspx>

cheers Darrel

 

[regani]

Mike I think it may be health and safety considerations, most/all? the low range pH indicators (Bromophenol Blue, Methyl Yellow, Congo Red etc) are aromatic compounds, and you don't find many old organic chemists.

Do I sense a case of uninformed chemophobia here?

All indicators are aromatic compounds and most dyes, synthetic and natural, are; it's kind of a requirement for colour (unless we are talking pigments). As are many other compounds, e.g. the lignin in wood, vitamin E, almost all antioxidants in the so called heath foods, a few of the amino acids and all of the nucleotides life is made from....
I know quite a few old organic chemists and hope to make it quite a fair bit past requirement myself

 

[dw1305]

Hi all,

Do I sense a case of uninformed chemophobia here?

I think you probably do, but you can never be too careful: <http://www.dhmo.org/facts.html>

I used to share an office with an organic chemist who kept a large vat of "dry cleaning" fluid. He used to dunk his ties etc in it when they needed cleaning, and I've never really recovered.

I know quite a few old organic chemists and hope to make it quite a fair bit past requirement myself

Hope you do, I believe old age is better than the alternative.

cheers Darrel

 

[regani]

I used to share an office with an organic chemist who kept a large vat of "dry cleaning" fluid. He used to dunk his ties etc in it when they needed cleaning, and I've never really recovered.

Argh, that seems like an extreme - and hazardous - case of chemical unconcernedness, no wonder you are scarred for life

 

[Mike Wise]

Reminds me of the time I was drilling de-watering wells for a future uranium open pit mine on a deposit that I'd delineated. The water was so clear and cold - and I was so hot and thirsty. Yes, it tasted GREAT! Maybe that's what gave me my "glowing personality"!