# New TDS pen.



## curefan (23 Nov 2012)

Hi....
I just got a new TDS pen today and was wondering does it need to be calibrated before the first use?

Also it says to rinse it in distilled water after every use. Is this important and will 4DKH water do?

Thanks, Dave.


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## jack-rythm (23 Nov 2012)

Can I ask where you got that from?

Sent from my GT-I9100 using Tapatalk 2


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## curefan (23 Nov 2012)

jack-rythm said:
			
		

> Can I ask where you got that from?
> 
> Sent from my GT-I9100 using Tapatalk 2



Well i bought it on ebay....first i ordered one from China and it never came, so I just ordered from a UK seller and it was in Ireland in 2 days!
There are plenty of them on ebay....I just picked one that came with the calibration solution.


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## dw1305 (23 Nov 2012)

Hi all,
They don't really need calibration, that is the great joy of them. Although they claim to be TDS pens (TDS is "total dissolved solids"), they really measure electrical conductivity, and then use a coefficient (some-where in the range 0.5 to 0.64)  to "convert" conductivity in microS into ppm TDS, <http://www.tdsmeter.com/products/calibrationsolution.html>. If you have the calibration solution you can check the meter occasionally, but they work pretty reliably.

The meter operates on a really simple method, there are 2 electrodes and a current is passed between them. Pure H2O is an electrical insulator and what we call "water" is really a dilute solution of one or more salts. The relationship between salts (as their ions) and conductivity is linear, so TDS gives you a measure of the total number of ions.

Washing in distilled water between uses is just to flush out any ions, 4dKH solution wouldn't do, but if you don't want to buy a bottle of DI water, you could use rain water.

cheers Darrel


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## jack-rythm (23 Nov 2012)

Seems a silly question but if you were to fin out your TDS readings were not the readings you wanted how would you lower/raise the TDS level?


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## gmartins (23 Nov 2012)

RO water for dilution. 
Any salt that you add to the water will increase TDS.

However, you should really consider why do you want to change your TDS.

GM


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## jack-rythm (23 Nov 2012)

Just thinking aloud. If u wanted crystal shrimp and your TDS was wrong how would you go about it.

Cheers

Sent from my GT-I9100 using Tapatalk 2


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## REDSTEVEO (23 Nov 2012)

I have a Microsiemens (electrical conductivity) meter which I used to use to make sure there was as little amount of TDS in the water as possible when I was breeding Discus Fish. The TDS (salts) used to penetrate the eggs and make them all go white even though they had been fertilised.

All this was before I started with EI and growing plants.

Steve


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## curefan (23 Nov 2012)

dw1305 said:
			
		

> Hi all,
> They don't really need calibration, that is the great joy of them. Although they claim to be TDS pens (TDS is "total dissolved solids"), they really measure electrical conductivity, and then use a coefficient (some-where in the range 0.5 to 0.64)  to "convert" conductivity in microS into ppm TDS, <http://www.tdsmeter.com/products/calibrationsolution.html>. If you have the calibration solution you can check the meter occasionally, but they work pretty reliably.
> 
> The meter operates on a really simple method, there are 2 electrodes and a current is passed between them. Pure H2O is an electrical insulator and what we call "water" is really a dilute solution of one or more salts. The relationship between salts (as their ions) and conductivity is linear, so TDS gives you a measure of the total number of ions.
> ...




Is the reason you can rinse in rain water because there is no additives in it unlike from your water supplier???

I just tested my tank water for the first time and I got a reading of 570 (my tap water reads 80). I think this is too high for CRS. EI dosing is probably increasing it.

So its kinda catch 22......reduce my dosing which may affect the plants or continue as is but cant have CRS!!!

What do ye think???


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## dw1305 (24 Nov 2012)

Hi all,


> Is the reason you can rinse in rain water because there is no additives in it unlike from your water supplier???
> I just tested my tank water for the first time and I got a reading of 570 (my tap water reads 80). I think this is too high for CRS. EI dosing is probably increasing it.


Yes, rain water should be low in salts, but even if you haven't got any low salts water, if you give a the probe a good swirl in the water you are testing, before taking the reading, it should be OK. 

Opinions will differ about your waters suitability for CRS, but I think we would all agree that you are right about the TDS value being because of EI. Personally I'd stop EI & go low tech. (but I don't use CO2, don't grow carpets and aren't interested in maximal growth) and use the "Duckweed Index" <http://www.ukaps.org/forum/viewtopic.php?f=27&t=21003> to fertilise your plants.

I think with regular water changes you should be able to keep the TDS around 120 - 150ppm. 

I use rain-water, but have a hard tap supply, keep soft-water fish and I change about 10% of the tank water every day. I can then just manipulate the proportions of rain and tap to keep the conductivity about 70 - 100 TDS. 

I don't try and measure anything else, and I just use the condition of the floating plants to tell me when nutrient levels are very low. I think this is a really easy approach to keeping shrimps etc, as it gives you tank stability and I think for the trickier fish and shrimp etc. stability is the key.

cheers Darrel


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## curefan (24 Nov 2012)

dw1305 said:
			
		

> Hi all,
> 
> 
> > Is the reason you can rinse in rain water because there is no additives in it unlike from your water supplier???
> ...




hmmm, dont really want to go low tech.....I like my planted carpets!!!
Might have to go for less demanding shrimp than CRS, even though i  had my heart set on them   

Would it help the TDS if i did not add in my ferts dry (as i do) and diluted them first in water???


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## AverageWhiteBloke (24 Nov 2012)

> Would it help the TDS if i did not add in my ferts dry (as i do) and diluted them first in water???



It doesn't matter if you dilute them once in the tank they are in and will increase the total sum of dissolved salts regardless of how you administer them. 

What size of a tank are we dealing with? Dosing EI values won't increase your hardness levels by a significant amount. You shouldn't have to add magnesium so you can take that out which will reduce the amount of salts a little. RO units are more reasonably priced these days. Some LFS will sell RO/pure water but making your own will work out cheaper in the long run. If the tanks not that big API do a water purifier with resin in to strip out minerals for around £40 or you could collect rain water which seems in abundance lately   If you go down the rainwater router would probably be an idea to filter it over some active carbon first. Rain water picks up plenty of other industrial nasties on the way down depending on where you live.


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## curefan (24 Nov 2012)

AverageWhiteBloke said:
			
		

> > Would it help the TDS if i did not add in my ferts dry (as i do) and diluted them first in water???
> 
> 
> 
> ...



My tank is about 570L. If I stop dosing Mgso4 ill be just left dosing KNO3,  KH2PO4 and trace elements.....Is that sufficient for the plants???


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## dw1305 (24 Nov 2012)

Hi all,
Unless you live in N. Ireland basalts, you need to keep the magnesium, Ireland is mainly old red sandstone, carboniferous limestone, shale and mill-stone grit and Connemara granite and none of them provide much magnesium to the gorund-water. Plants have a reasonably high magnesium demand, as it is the central atom of the chlorophyll molecule.

If you live in a dairy farming area ask the local farmers if "Grass Tetany" (hypomagnesaemia) is a problem, if they have to provide a salt block for it, you can be pretty sure there isn't much magnesium in your water.

cheers Darrel


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## AverageWhiteBloke (24 Nov 2012)

I would say ro water would work out the best value with a tank that size or get red cherry shrimp. Just as much fun but a bit more tolerant of water hardness.


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## Ady34 (25 Nov 2012)

Hi,
I want to know your dosing regime as a rise from 80ppm tds to 570ppm is huge. Is that by the end of the week before a water change? My tap water is just shy of 80ppm from the tap, i add ca and mg to my water change water and dose ei and at the end of the week its only around 220ppm max! 
Do you also have rocks which effect water chemistry such as seiryu which could be adding to the TDS readings your getting?
Cheerio,
Ady.


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## viktorlantos (29 Nov 2012)

Calibration solution is not expensive and you can use it when you're unsure everything is ok. But as others said TDS pens are usually stable. If they are decalibrated a little the difference is usually so small that even your CRS shrimps will not worry about that. Just shake down the remaining water between 2 measures as the water on the pen could give you a wrong result.

Target TDS above 100 or 120 below that you will see molting problems

If you go with CRS CO2 helps you to keep your water stable for them. Otherwise pH changes will be a hassle all the time. If you do not use CO2 then use some media which lowering your pH. Better to be on the lower side then always surf on the upper limit


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