# TDS Parameters



## BarryH (2 Apr 2020)

I see a number of posts on UKAPS mentioning TDS parameters. Not knowing or testing the TDS on my only tropical tank, can I ask how important these are?

In the tank, tap water with Prime added, I have a small shoal of Harlequin Rasboras and a small but rapidly growing group of Red Cherry shrimp. To the tank I add various dried and frozen foods for the fish and food that includes Bacter AE for the shrimp. I'm sure this is all going to have a bearing on the TDS within the tank and I'm starting to think maybe it's time I should take notice of it.


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## dw1305 (3 Apr 2020)

Hi all,





BarryH said:


> I'm sure this is all going to have a bearing on the TDS within the tank and I'm starting to think maybe it's time I should take notice of it.


You could definitely use a TDS (Conductivity) meter to find out if your TDS is rising over time. If it is, it suggests you may need to <"change a bit more water">. 

The advantage of conductivity measurement is that you can buy a relatively cheap meter, dip it into any tank water and it instantly gives you an accurate reading. There isn't <"another dip meter or test that does that">, they all need calibration etc. The disadvantage is that it doesn't tell you what ions you have, just how much electricity they are conducting. 

The other real disadvantage is that there isn't a single "good" datum range, your initial conductivity value is going to depend largely on how hard your tank water is. 

As an example DI water from the lab. is going to be about 1 microS, the rain-water I use ranges between about 30 microS (winter) and 150 microS (late summer) and our tap water from about <"600 to over 700 microS"> (largely limestone aquifer water). The ions in the rain and tap water are largely calcium (Ca++) and bicarbonate (HCO3-), so in terms of plant nutrietion you can mainly ignore them.

cheers Darrel


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## Witcher (3 Apr 2020)

dw1305 said:


> The advantage of conductivity measurement is that you can buy a relatively cheap meter, dip it into any tank water and it instantly gives you an accurate reading.


Hi Darrel, what popular salt/substance would you suggest to test if all ok with them? I mean making buffer solution or sth similar of known TDS.


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## dw1305 (3 Apr 2020)

Hi all, 





Witcher said:


> Hi Darrel, what popular salt/substance would you suggest to test if all ok with them? I mean making buffer solution or sth similar of known TDS.


Potassium chloride (KCl) is the normal one. The working are in <"simple and fail-safe.....">.

I make up this as a calibration solution for conductivity meters on a fairly regular basis, but we buy in pH calibration buffers, because they are much more time consuming to make.

cheers Darrel


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