# Are my TDS readings on the high side?



## Quetzalcoatl (22 Apr 2012)

I am currently using a G6 filter and I am taking my readings from the built in Conductivity Reader. I have noticed that TDS readings are around 650 immediatly after a 50% water change and increase throughout the week peaking at around 850 by the time water change comes around again. 
I understand that TDS readings will increase as I dose E.I, inject Co2 etc throughout the week, but are my readings high at the initial 650 mark? 
This is something that has been bugging me for some time. Should it be, or is it not all that important? I have steady growth, but nothing exceptional, I just can`t help think that this could be a limiting factor in my system?

Help please.


----------



## Antipofish (22 Apr 2012)

That is not a TDS reading mate.  Its a conductivity reading which is different.  The changes can be used (in part) as a reflection of changes in TDS between water changes.  Mine used to increase by 40 between changes (which were twice weekly and 50%).  Its better to use it as an indicator rather than anything really meaningful in a planted tank.


----------



## ceg4048 (22 Apr 2012)

Quetzalcoatl said:
			
		

> I understand that TDS readings will increase as I dose E.I, inject Co2 etc throughout the week, but are my readings high at the initial 650 mark?


Yes, the reading is high to extremely high. It's probably too high to breed soft water fishes on a regular basis, or to grow a 1/2 dozen or so species like Tonina, so if any of these are your objective then you might think about cutting the tap with RO. EDTA chelated traces often precipitate and this is indicated by  clouding of the water shortly after dosing.

Here is an example of a tank at 850 microsiemens. I really don't see why you need to worry otherwise. If you want exceptional growth add more of everything, especially CO2. CO2 application is the limiting factor in 99.999% of all tanks.






Cheers,


----------



## Quetzalcoatl (22 Apr 2012)

Ceg.  Awesome plant health.  

As for adding more Co2. I think I am at my limited in regards to fish welfare! I increased injection rate recently and witnessed stress on the inhabitants. I had to back off a bit as figured it was going to end bad.   
Current E.I mix is KNO3 (30g) - KH2PO4 (30g) - Trace (8g) in 1000ml solution. Could I look at adding more KNO3 to a modertely planted 180ltr. Co2. 2x39watt T5, or am I dosing high already? The extra KH2PO4 was to combat GSA which has worked a treat.  

Chris. I thought that the Conductivity meter reading gave a "indirect" measure of TDS or ions in the water. This is what Fluval advertised as a feature of the G6. Forgive my ignorance in understanding the science behind conductivity and TDS and the difference between the two. Care to teach me?


----------



## Antipofish (22 Apr 2012)

Quetzalcoatl said:
			
		

> Ceg.  Awesome plant health.
> 
> As for adding more Co2. I think I am at my limited in regards to fish welfare! I increased injection rate recently and witnessed stress on the inhabitants. I had to back off a bit as figured it was going to end bad.
> Current E.I mix is KNO3 (30g) - KH2PO4 (30g) - Trace (8g) in 1000ml solution. Could I look at adding more KNO3 to a modertely planted 180ltr. Co2. 2x39watt T5, or am I dosing high already? The extra KH2PO4 was to combat GSA which has worked a treat.
> ...



I dont fully understand it either. But going on what George told me, they are not the same thing, but as I said, changes in conductivity can include an indication of changes in TDS.  I am sure there is a thread about it on here somewhere.


----------



## George Farmer (23 Apr 2012)

Here's a basic description of conductivity -

viewtopic.php?f=38&t=19495&start=60#p203451

TDS is similar, but a measurement of physical stuff dissolved in the water. 

Conductivity measures how much stuff in reference to how much electricity it will conduct.

A basic example of how they differ -

Imagine pure water with a tiny qty of dissolved metals.

The TDS may be relatively low because the physical qty of stuff is low.

The conductivity may be relatively high because the metals conduct electricity.

Like Clive says, it's not really an issue unless you're growing/keeping specific fish and plants.


----------



## Ady34 (23 Apr 2012)

Hi,
i tend to ignore my actual G6 conductivity reading (for fish water needs) now as buffers and ferts change it, however as Antipofish said, use it as a guide for changing water perameters which, with quick action, could prevent an algae outbreak or fatalities. Youll get used to what is a 'normal' weekly reading, and change in reading, so anything outside this means potential trouble. A 200 change does seem large, however i dont know how much EI ferts change it as ive been using TPN+, and have only yesterday started using a salts fert mix. I also imagine it is dependant on how much ferts you are adding as to the weekly increase in conductivity.
Cheerio,
Ady.


----------



## dw1305 (23 Apr 2012)

Hi all,
Yes, they are  high, but if you have a very hard supply the dissolved calcium carbonate will mean that you start at >500 microS conductivity, like George's link says. 

I'll just use conductivity, because all TDS meters are conductivity meters. To actually measure TDS, you have to evaporate a known weight of pre-filtered water, and weigh what is left after evaporation (usually you do this by filtering/evaporating in a special funnel, with a filter paper to collect the TDS on) <http://www.norweco.com/html/lab/test_methods/2540cfp.htm>.

Because of this you know that the meters measure electrical conductivity (in microS), and then use a conversion factor to approximate this to ppm TDS. The G6 documentation should tell you what the factor is, but it will be somewhere in between 0.5 (100microS = 50ppm TDS) and 0.64 (100microS = 64ppm TDS).

cheers Darrel


----------



## dw1305 (23 Apr 2012)

Hi all,


> Youll get used to what is a 'normal' weekly reading, and change in reading, so anything outside this means potential trouble.


 Should also have said that "Ady34" is right, and that the number you start with will depend upon how much fertiliser you add (conductivity is a measure of the soluble salts as ions, plants can only take up nutrients as ions, more fertiliser = more TDS), as well as the water you start with. 

I just dip the meter in occasionally and if the number is higher than I expected I change a bit more water (with rain-water), and if it is lower I add a little bit more tap (17dKH).

cheers Darrel


----------



## ceg4048 (23 Apr 2012)

Quetzalcoatl said:
			
		

> ...As for adding more Co2. I think I am at my limited in regards to fish welfare! I increased injection rate recently and witnessed stress on the inhabitants. I had to back off a bit as figured it was going to end bad..


 So then the next thing on the list, as always, is to look at whether your lighting is too intense and whether your flow/distribution is inadequate. You also need to look at the timing of your gas.

Cheers,


----------



## Quetzalcoatl (23 Apr 2012)

Thanks guys. That`s mades things alot clearer. I thought I had read that conductivity, and TDS were kind of similar but was unsure of the connection. I understand the science behind it now.  



> Yes, they are high, but if you have a very hard supply the dissolved calcium carbonate will mean that you start at >500 microS conductivity


Hi Darrel. I always thought that my water was soft? Reading through my water report it states that Conductivity is 233 microS what could be causing it to register at 650 immediately after a weekly 50% water change?
Any chance of casting a scientific eye over my report. Is there anything out of the ordinary that I should be concerned about? I`ll be honest, I`m unsure what the report is telling me. And what I should be looking for.   A little pointer in the right direction would be very much appreciated.  
http://www.unitedutilities.com/waterquality.aspx Don`t understand why the link won`t take you direct, you will have to enter postcode CW124RG.
Would I benefit dosing CaCO3 if my supply is soft? Also I stopped dosing MgSO4 as I thought it wasn`t needed.


----------



## Antipofish (23 Apr 2012)

Liam do you have any rocks or substrate in there that would contribute to that reading ?  What is your substrate and hardscape ?


----------



## Quetzalcoatl (23 Apr 2012)

Hmmmm. Don`t laugh! Substrate comprises of Flourite, sand, Akadama, Molar Clay, and Knott Nature soil. (In that order) The initial tank has been a bit of an evolution from first time fish keeper (hence the sand), to planted tank enthusiast. (hence the Knott) I am going to break it down and attempt a proper scape when I`m happy/confident that I know enough to achieve a successful scape! Hardscape is minimal, bit of bogwood, and a couple of pieces of Welsh slate. God this sounds awful.


----------



## Antipofish (24 Apr 2012)

Quetzalcoatl said:
			
		

> Hmmmm. Don`t laugh! Substrate comprises of Flourite, sand, Akadama, Molar Clay, and Knott Nature soil. (In that order) The initial tank has been a bit of an evolution from first time fish keeper (hence the sand), to planted tank enthusiast. (hence the Knott) I am going to break it down and attempt a proper scape when I`m happy/confident that I know enough to achieve a successful scape! Hardscape is minimal, bit of bogwood, and a couple of pieces of Welsh slate. God this sounds awful.



Not really, Some others on here have complete mixes of this and that and it doesnt really matter what the subtrate is anyway, to grow plants.  Some help them on their way, but you dont really need anything special.  Its all to do with light Co2 and ferts as you already know I am sure .

I don't know about the flourite, but the rest would not contribute to such a high conductivity I would not have thought.  Again, I don't know about slate.  I do know that Seiryu stone can do.  I was hoping for something obvious to jump out at me but I cannot really say, sorry.  Perhaps someone who knows better will comment.  Just trying to see if there was something in there that would give rise to your readings compared to what the water report (which could be wrong in terms of micro locality) suggests.


----------



## George Farmer (24 Apr 2012)

dw1305 said:
			
		

> Hi all,
> Yes, they are  high, but if you have a very hard supply the dissolved calcium carbonate will mean that you start at >500 microS conductivity, like George's link says.
> 
> I'll just use conductivity, because all TDS meters are conductivity meters. To actually measure TDS, you have to evaporate a known weight of pre-filtered water, and weigh what is left after evaporation (usually you do this by filtering/evaporating in a special funnel, with a filter paper to collect the TDS on) <http://www.norweco.com/html/lab/test_methods/2540cfp.htm>.
> ...


Hi Darrel,

So TDS and conductivity are the same, just different units. In that case I apologise for my incorrect assumption that they were different. This was based on how much my conductivity would rise when adding an iron-based fertiliser when compared with a rich macro mix.


----------



## dw1305 (24 Apr 2012)

Hi all,
Got it, it is an *.asp page, so it is created from your enquiry to a data-base on the fly, rather than being a static page.

 
Hardness       -         6.650 Clark		
Calcium	     -        30.3mg Ca/l
Conductivity  -	233uS/cm at 20oC
Magnesium    -	4.44mg Mg/l
Nitrate	    -     9.57mg/l
Sodium -	24.9mg/l
Look quite good actually, the hardness is in Clark, 





> _A Clark degree (°Clark) or English degrees (°e or e) is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm._


 which is equates to 1degree Clark = 0.8dKH, so about 5dKH. 

Calcium and magnesium look OK (30ppm Ca and 4.5ppm Mg), but I'd probably go back to adding some MgSO4.7H2O, but you don't need to add any calcium. About 10ppm NO3 (lower than most water in the UK), and the sodium is quite high at 25ppm.


> Reading through my water report it states that Conductivity is 233 microS what could be causing it to register at 650 immediately after a weekly 50% water change?


 Now that is the difficult question, because conductivity just tells us the charge carrying ions. I haven't worked it out yet but my suspicion would be that the elements listed can account for all the conductivity in the tap water, so it is either the EI salts (which are all soluble) most probably in combination with the cations being exchanged back into solution (for H+ ions) by the media with CEC - fluorite, moler clay, Akadama or "Knott's nature soil".  Assuming that the "nature soil" contains added nutrients, that would be my choice for the source of the extra conductivity. <http://www.ukaps.org/forum/viewtopic.php?f=17&t=14123>.



> This was based on how much my conductivity would rise when adding an iron-based fertiliser when compared with a rich macro mix.


 Iron is a bit of a funny one, as it doesn't contribute to the conductivity when it is chelated, the same happens with adding urea, it doesn't have a charge, so it doesn't raise conductivity.

cheers Darrel


----------



## Quetzalcoatl (24 Apr 2012)

Thank you very much for taking the time to analyze my water parameters Darrel. It`s very much appreciated.  


> About 10ppm NO3 (lower than most water in the UK), and the sodium is quite high at 25ppm.


I am currently adding 30g of KNO3 and 30g of KH2PO4 to 1000ml tap water for Macro solution. As my NO3 appears to be below average, would I benefit from increasing KNO3, what would my current dosing equate to in regards to ppm. Apologies for all the questions, but the science behind the hobby is where I fall down.  
I remember I was adding about 50g of MgSO4. I`m due to mix some fresh ferts this week. I will introduce the Magnesium back into my dosing and see if things improve!
Thanks again pal.


----------

