Conductivity

Hi,
is there anyone on the forum who has a conductivity meter?
Regards,Tim

I have a very expensive mutimeter that does conductivity (4.5 digit, .05% accuracy etc...), but I do not have the probe set for water use, just the normal ones. What do you need to measure, and how often?

would'nt a tds meter do ?

murph wrote:

I have a very expensive mutimeter that does conductivity (4.5 digit, .05% accuracy etc...), but I do not have the probe set for water use, just the normal ones. What do you need to measure, and how often?

Hi,
just want to find out what coductivity my tab water has.One test will do me.
Regards,tim

Damian_Ireland wrote:

would'nt a tds meter do ?

Have the TDS done.Need the conductivity.Thanks,Tim

Ok. Will rtfm and see how the normal probes corrosponde to the liquid ones. It's just a matter of surface area and distance.....(and maths).

Was does conductivity tell you, what does high or low levels mean, I thought it was a mainly a marine measurement, I am interested to know the relevance in freshwater.

Daragh

I've only ever used conductivity for freshwater and never for marines.
But, I'm old school I suppose.
Back to the 70s etc etc when we would often use conductivity for freshwater (but not for most of the fish in captivity though).

The thing is that it is just another reading to go along with other readings; in freshwater it is important to balance what the conductivity really means with respect to the other readings that are taken.
Just like a pH reading on its own is of little real use to tell you the real state of play wrt acid/base balance...it simply gives a pH at that time; conductivity simply gives the...conductivity (ie the bulk-phase action of electrolytes) at that time.

It depends on how the data is interpreted in freshwater that makes conductivity measurements either useful or useless. It also has uses in 'treated' water (eg RO).

ian

Daragh_Owens wrote:

Was does conductivity tell you, what does high or low levels mean, I thought it was a mainly a marine measurement, I am interested to know the relevance in freshwater.

Daragh

I hope my english is good enough to explain to you what I am after.
Over the conductivity you can get also another conclusion over your TDS in your water.In the most waters the conductivity is caused through salts.As a guide: 1 Gh has a conductivity of 33 uS/cm.(avarage water).So I should get with 10 Gh a reading of 330u/cm but if I get a reading of for example 420u/cm that would mean that there are alot of other salts in the water than the calcium and magnesiumsalts.There could be for example natrium(Sodium) or kaliumsalts(Potassiumsalts) in it.So if I have a reading of 10 Gh and you have a reading of 10 Gh we still could have a way different conductivity what our normal drop test doesnt recognise.The conductivity/TDS is responsible for the osmose pressure in the water.Through the osmose ,freshwater fish dont drink.Water is permantly penetrating into the fish and out through the cidneys.The osmose pressure is responsible for widening or shrinking of the cells.If the pressure changes slowly,most of the fish or plants can adjust to it-but often not the egg or spermcells.Often a problem in not succesfull breeding of softwaterfish in harder water.
Now to my practical problems what I try to solve.I realised my frontosas scratching themselves on the sand more than I think it would be normal(they have no worms in the gills and no bacterial infections on the skin)maybe it is the osmose pressure what they dont like and thats why they feel "itchy".The other problem is that something in my water doesnt allow me to rise the Gh higher than 10.When I harden my water from 2 Gh to 10 with additives works with no problems.When I give more salts in, I still get the same readings(test done with 3 different test kits) -so no further increase of the Gh. The salts are not desolving anymore or something else in the water is falling in part or buffering my Gh.(white paticles are swimming on the surface of the water).Maybe the water is "full"(very high conductivity)......So thats why I want to get a conductivity reading.
P.s.Some Fishkeepers in Germany take the conductivity as an idicator for waterchanges.It is just another parameter to let us know more about the water we have.
Regards,Tim

frontosa wrote:

Daragh_Owens wrote:

Was does conductivity tell you, what does high or low levels mean, I thought it was a mainly a marine measurement, I am interested to know the relevance in freshwater.

Daragh

I hope my english is good enough to explain to you what I am after.
Over the conductivity you can get also another conclusion over your TDS in your water.In the most waters the conductivity is caused through salts.As a guide: 1 Gh has a conductivity of 33 uS/cm.(avarage water).So I should get with 10 Gh a reading of 330u/cm but if I get a reading of for example 420u/cm that would mean that there are alot of other salts in the water than the calcium and magnesiumsalts.There could be for example natrium or kaliumsalts in it.So if I have a reading of 10 Gh and you have a reading of 10 Gh we still could have a way different conductivity what our normal drop test doesnt recognise.The conductivity/TDS is responsible for the osmose pressure in the water.Through the osmose ,freshwater fish dont trink.Water is permantly penetrating into the fish and out through the cidneys.The osmose pressure is responsible for widening or shrinking of the cells.If the pressure changes slowly,most of the fish or plants can adjust to it-but often not the egg or spermcells.Often a problem in not succesfull breeding of softwaterfish in harder water.
Now to my practical problems what I try to solve.I realised my frontosas scratching themselves on the sand more than I think it would be normal(they have no worms in the gills and no bacterial infections on the skin)maybe it is the osmose pressure what they dont like and thats why they feel "itchy".The other problem is that something in my water doesnt allow me to rise the Gh higher than 10.When I harden my water from 2 Gh to 10 with additives works with no problems.When I give more salts in, I still get the same readings(test done with 3 different test kits) -so no further increase of the Gh. The salts are not desolving anymore or something else in the water is falling in part or buffering my Gh.(white paticles are swimming on the surface of the water).Maybe the water is "full"(very high conductivity)......So thats why I want to get a conductivity reading.
P.s.Some Fishkeepers in Germany take the conductivity as an idicator for waterchanges.It is just another parameter to let us know more about the water we have.
Regards,Tim

Tim, hope you don't mind me just translating two bits of chemistry into english.....'natrium' (=Sodium salts); 'Kaliumsalts' (= Potassium salts). Other than that you're post makes perfect sense. I don't speak German BTW.

Although I've mislaid all my conductivity meters during recent house moves, I would have, like you quote german fishkeepers do, use conductivity meters as an indicator to change water in freshwater tanks.
In the days of keeping Marines, I never used them for routine testing...but would have used them for testing the various salt-mix formula under development.

Not at all,Ian.Thanks for that.I edited into my post.
Regards,Tim

frontosa wrote:

Not at all,Ian.Thanks for that.I edited into my post.
Regards,Tim

From years of translating german chemistry research papers, I found most chemical names ae almost the same in english as they are in german (which is useful as I don't speak german).....but a few (eg sodium and potassium) have very different common names.

ian

Thanks for the info, I thought conductivity was directly related to TDS, so that is interesting.

Is ORP related to Conductivity? I bought an ORP meter at one stage but could not find any understandable information in relation to freshwater fishkeeping.


Daragh

A big thanks to Xeon and Seahorse Aquariums for the assistance in my research (got conductivity readings)
Will keep yee updated when I find out more.
Regards,Tim

Daragh_Owens wrote:

Was does conductivity tell you, what does high or low levels mean, I thought it was a mainly a marine measurement, I am interested to know the relevance in freshwater.

Daragh

Conductivity: Conductivity or “k” is the measure of an aqueous solutions ability to carry an electric current.
This is dependant on the presence of ions, the concentration of the ions, their mobility and valence and the temperature at which the measurement is taken. Inorganic compounds are generally better conductors than organic (non-dissociative) ones.

(i.e. the measurement of conductivity is generally for inorganic salts, the most common of which is NaCl)

Measurement of conductivity is by spatially fixed and chemically inert electrodes. The conductance of a solution (G) is directly proportional to the electrode surface area (A, in cm2), and inversely proportional to the distance between the electrodes (L, in cm). Conductivity (k) is therefore the constant of proportionality, i.e;
G = k(A/L)

(i.e. the way an electrode works and reads conductivity when placed in a sample)

The units of k are ohm/cm or µmho/cm, however in the SI unit system, it is the reciprocal, which is used, the siemens (S)or micro siemens (uS).

(i.e. What the measurement is)

The conductivity of ultra pure water at 18oC is very low, at approximately .0037µS/cm, with distilled at .5-2 µS/cm. Conductivity in surface waters (natural waters, but in an irish context) should fall within 50-1000µS/cm, whilst water above 1500µS/cm is deemed unsuitable for agricultural uses etc. The Irish EPA set limits for surface waters and potable waters at 1000 & 2500 µS/cm respectively measured at 20oC. They also suggest that the following formula is a good approximation of total dissolved solids in surface waters;

Conductivity (uS/cm) x 2/3 = Total Dissolved Solids (mg/l)

The most common method for determining salinity is via a reading of a samples conductivity. Using a formula we can then work out the [NaCl] in mg/l. Thus;

Mg NaCl/l = (f)(x)

Where x is the specific conductivity in uS/cm, and f is the conversion factor. At a [NaCl] range of 0-100mg/l NaCl, f = .52, and above this f = .55.

Just as a definition, i hope im not repeating whats already been said!

Felim i followed this post and thought i got the idea but after reading your post all i can say is WHAT?????, for the non scientific of us can you break this down into an idiots guide

sheag35 wrote:

Felim i followed this post and thought i got the idea but after reading your post all i can say is WHAT?????, for the non scientific of us can you break this down into an idiots guide

Sorry there, i put a couple of i.e.'s in. Hope that helps, i was just offering a quick bit of info. just trying to show conductivity used in both fresh & saltwater measurements, and what is actually being measured directly. Im sure there are many reasons why different people would be interested in this parameter!

a little clearer thanks, but i'm still no scientist

Felim, thanks you for the detailed post, maybe I asked the wrong question, can you explain what it means to a fish keeper. I don't really need to know (I do but don't understand!) what it is measuring or how, but what the affects of a high or low reading are to fish or what it indicates. Or scenarios when a high or low reading would be required etc.

I use temperature measurements all the time and I don't know how it is calculated but I do know what the results mean, I am trying to get to the same position here with conductivity.

By the is ORP related to conductivity?



Daragh

Daragh_Owens wrote:

Felim, thanks you for the detailed post, maybe I asked the wrong question, can you explain what it means to a fish keeper. I don't really need to know (I do but don't understand!) what it is measuring or how, but what the affects of a high or low reading are to fish or what it indicates. Or scenarios when a high or low reading would be required etc.

I use temperature measurements all the time and I don't know how it is calculated but I do know what the results mean, I am trying to get to the same position here with conductivity.

By the is ORP related to conductivity?



Daragh

Hi darragh, well i can only speak, in relation to the irish context, and what it usually means in our surface waters, and i dont want to repeat something someone else has already said. Like one of the posters alluded to in the first page, conductivity is of little importance by itself (as in my opinion is redox pot.)But as a lot of people use tap water, and tap water is from our surface waters, you could use conductivity as a rule of thumb measurement. Any other conclusions based on this measurement would need to be backed up by a suite of data on numerous parameters.
One practical direct use of conductivity is when ecologists use it to measure what current they need to stun fish safely in surveys, or say a river dried up (which does happen in ireland) and you want to move fish upstream. In this regard it is direct.

I really only used conductivity as a precursor measurement to determine ranges for Alkalinity/Hardness by wet titration method/Flame Atomic Absorption Spectrometry resp, and in general (but certainly not always) you could say that with higher conductivity, you have a better chance of your water having a half decent buffering capacity. That is your waters own inate ability to absorb acidity without any major drop in pH. Therefore, if you have a low conductivity, it may be less likely that your water will be able to assimilate acidity, and may lead to drops in pH.

The alkalinity can be caused a lot by carbonate species, hydroxide, ammonia, and many others in small and variable amounts, the "Hardness" will mostly be caused by Calcium and Magnesium species.

Obviously dissolved minerals etc are involved in osmotic pressure also, for instance that is why cells/microorganisms are not diluted in water, as this would lyse them. Ringers diluent or other solutions are used as buffers to even out osmotic pressure in these cases.

So is it related to Redox potential? I wouldn't want to be the person who answers this definitively. All the chemistry in water is related in some way. To define a relationship between two vague bulk measurements, you would need lots of other tests over a period of time, and even then, they would only relate to the water supply tested. Unless someone i dont know about has come up with a magic formula.


Also on a side note, if you are talking about osmoregulation in fish, i would be more interested in Aluminium levels in the water. It is toxic, and not only do certain places have high Al in the surface waters, but the Al is used in drinking water treatment as a floculant. This is exacerbated in areas with low calcium levels, as the speciation of Al will be determined by pH to a great degree.

Anyway, im off, hope that is of some help!

If you are drunck and test the conductivity holding a multimeter probe in the left hand and one the the right hand if you set the multimeter to the right resintancee level you can actually detect a difference in conductivity between being sober and druck!!: This measurement in completely useless for testing druckness accurately, that's why we have alcohol blood test.

With the same logic testing conductivity in enclosed aquarium systems is completely academic or googleilic. The real test is redox level this is gives a real time snap shot of the real state of the enclosed water system. I have been running a Tunze redox meter 24/7 on a african fresh water tank for over a year now when the redox level drop to 205mv it starts a ozone and air pump injecvting into the sump which increased the redox to a predetermined safe level then it cuts off again, this also keeps the water gin clear (without doing water changes to dilute the yellow colour)a noticble improvemnt was notice in Tropius Dubois with one week of this water treatment.

Great, some info on redox. I could never get a handle on its function in freshwater. I had a redox meter but found the result varied considerably from tank to tank even though they were stocked and treated similarly and could not find out the causes or the meaning. I also found that the same tank would give different readings when taken at different times of the day. From memory the redox levels were usually around 400, but it is a coupl eof years ago so I am not 100% positive. I bought an ozone generator and controller but after reading a few scare storied about ozone never used it, by what means to you introduce it into the tank to ensure that none is escaping?

I would be grateful of any more info on redox, what high or low reading indicate etc.



Daragh