# TDS plotting



## Soilwork (2 Feb 2017)

So what do we consider a large change in conductivity?

After 4 large water changes and sporadic dosing of EI macros (daily dosing) my TDS was stitting at 250ppm before the last water change.

After the water change (about 80%) it was 125ppm and now another day later is 138ppm.

My tap is 60-70ppm. Would you consider a 70ppm shift from a baseline 60-70ppm to equal by now approx 140ppm a large change in TDS?

Would my TDS sitting up at 250ppm indicate that my plants are not using many nutrients and that they are just accumulating? I change water every week, feed once a day and I'm lightly stocked. 

Thanks


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## Bert2oo1 (2 Feb 2017)

Following along here as I'm after the same answers 


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## dw1305 (2 Feb 2017)

Hi all,
It isn't a huge change in TDS. If you think that full salinity Sea Water is 53,000 microS, and one microS is about 0.64 ppm TDS, it only needs small addition of any salt to raise the TDS considerably.

The 0.01M potassium chloride (KCl) standard, that you use to calibrate the meter, is 1013 microS.

A molar solution of KCl is 74.6g made up to one litre with H2O (39.1(RAM K) + 35.5 (RAM Cl) = (74.6 RMM KCl).

So a 0.01M solution of KCl is 0.75g of KCl made up to one litre.

cheers Darrel


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## Soilwork (2 Feb 2017)

But what if we consider that Amazon black waters have very low TDS and my aquarium has a relatively low TDS and that the only things I add are flaked foods and fertilisers and that after 4x water changes at 50% plus my TDS is still double that of my tap. 

Assuming that these levels are not harmful to my softwater fish does this give any indication of how much fertilisers were actually being used in my aquarium?

Cheers


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## jolt100 (2 Feb 2017)

Soilwork said:


> But what if we consider that Amazon black waters have very low TDS and my aquarium has a relatively low TDS and that the only things I add are flaked foods and fertilisers and that after 4x water changes at 50% plus my TDS is still double that of my tap.
> 
> Assuming that these levels are not harmful to my softwater fish does this give any indication of how much fertilisers were actually being used in my aquarium?
> 
> Cheers


Hi, I think darrel has said in other posts that TDS meters only measure conductivity which depends on the concentration of ions in the water.  A very small amount of ions from any soluble salt will give a large increase in conductivity,  this includes the Ca and Mg which is in your tapwater, wastes from fish and plants and any salts added as fertilisers will put conductivity up immediately . 
The aim of EI is to have an excess of all the required nutrients and to replenish the excess after a water change so if your plants don't use all the salts, which is the required position, you will still see a higher conductivity in the tank at the end of the week than your tapwater. 
You can't really read too much into the figures,  black water habitat is very low in plant nutrition but has massive turnover and is not a closed system like a tank. Unless you are trying to breed some difficult fish species and are less concerned about plant growth conditions I wouldn't worry about TDS. Keep adding EI and regular water changes and give them time to adapt. 

Hope this helps 
John


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## Bert2oo1 (2 Feb 2017)

jolt100 said:


> Hi, I think darrel has said in other posts that TDS meters only measure conductivity which depends on the concentration of ions in the water.  A very small amount of ions from any soluble salt will give a large increase in conductivity,  this includes the Ca and Mg which is in your tapwater, wastes from fish and plants and any salts added as fertilisers will put conductivity up immediately .
> The aim of EI is to have an excess of all the required nutrients and to replenish the excess after a water change so if your plants don't use all the salts, which is the required position, you will still see a higher conductivity in the tank at the end of the week than your tapwater.
> You can't really read too much into the figures,  black water habitat is very low in plant nutrition but has massive turnover and is not a closed system like a tank. Unless you are trying to breed some difficult fish species and are less concerned about plant growth conditions I wouldn't worry about TDS. Keep adding EI and regular water changes and give them time to adapt.
> 
> ...



If the TDS is higher than you originally started with after a water change before dosing ferts etc, doesn't that mean that the ferts from the previous week have continued on to the next week? There for over say 5 weeks you will have a pretty large build up of excess ferts? 

If a 50% water change resets the system then shouldn't the TDS basically go back to the TDS of your tap level? 


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## sciencefiction (2 Feb 2017)

I have low tech tanks.

From experience in a non-dosed tank my TDS increase in a 7 day period is no more than 20- 30ppm at worst and after a 50% water change it gets back identical to tap water..I once didn't water change a tank for roughly 5-6 months. The TDS rose from 270ppm to 500-600ppm.  My fish did not like it. My plants loved it...

So I think that if your tap water is at 60-70ppm, a TDS of 250ppm is a huge increase and you're overdosing and your plants are not consuming as much as you think they do. This will further accumulate in time and can cause a variety of problems...So there's an obvious issue with the upkeep in my honest opinion, unless you want to raise your TDS a bit deliberately to a bit higher level and keep it there for other reasons....There's no need to let the water deteriorate so much otherwise....not good for your fish...


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## sciencefiction (2 Feb 2017)

Bert2oo1 said:


> If a 50% water change resets the system then shouldn't the TDS basically go back to the TDS of your tap level?



A 50% water change does not reset a system. You need 2-3 back to back 70-80% water changes to fully reset a tank and it should be done from time to time.....in any tank for the sake of preventing accumulation of any kind.....But generally, if you do a  50% water change each week you're still doing more water changes than most fishkeepers....



jolt100 said:


> A very small amount of ions from any soluble salt will give a large increase in conductivity, this includes the Ca and Mg which is in your tapwater, wastes from fish and plants and any salts added as fertilisers will put conductivity up immediately .



Yes, if you dose table salt in your water...or huge amounts of Ca and Mg salts..but why would one do that in the first place?
Practically, if you don't dose anything or much and you have healthy fishkeeping habits in terms of stocking, feeding and water changing, you won't see much change in TDS at all week from week and even a decrease in a planted tank...That's why I have always suggested one buys themselves a TDS meter and stops using liquid test kits of any kind..


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## Soilwork (3 Feb 2017)

Thanks all.

Bert as sciencefiction has alluded to the tank water will not reset but it will begin to stabilise at a TDS that is still higher than the tap.  The level it will stabilise at will depending on what we are dosing and how much.

Personally I don't want my Fertilisers to stabilise at a level considerably higher than what the plants can consume.  Especially micro nutrients (heavy metals)

@sciencefiction im confident in my maintenance routine and I perform regular water changes.  My problem is that I don't want gross amounts of unnecessary nutrients building up in my tank.  If my TDS is far off from my tap even after back to back large water changes then this surely must indicate I am in excess.

I realise this is the point of EI but I believe this excess of heavy metals in my very soft tap water GH 1.4 dGH re causing issues with both flora and fauna.


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## dw1305 (3 Feb 2017)

Hi all,





Soilwork said:


> Personally I don't want my Fertilisers to stabilise at a level considerably higher than what the plants can consume. Especially micro nutrients (heavy metals)





sciencefiction said:


> So I think that if your tap water is at 60-70ppm, a TDS of 250ppm is a huge increase and you're overdosing and your plants are not consuming as much as you think they do.


Yes I'd tend to agree.

I keep soft-water fish, and I like to keep the TDS fairly low. I can do this by adjusting the proportion of rain-water to tap in my tanks. I aim for the range 80 - 140 microS.

I don't add nutrients to the tanks regularly, I use the health and colour of the floating plants (these are not CO2 limited) to judge when to add nutrients. I've called it the <"Duckweed Index">, because I adapted it from the_ <"Lemna_ bioassay"> used with waste water.

cheers Darrel


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## AverageWhiteBloke (7 Feb 2017)

Surely other things like hard scape will make a difference. My tapwater is about 18ppm with nothing worth measuring regarding KH/GH with test kits but my tank sits at around 250ppm and the KH around 4dg. I can only assume that the three bits of stone in there gradually raise the KH and TDS as well as the other salts I dose. I change 50% weekly and the KH drops to 3dg raising back to 4 ish deg by the next change. So if nitrogen or phosphate is left over does this increase TDS or is it just the salt it transported in on? That's something I've often wondered.


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## Soilwork (7 Feb 2017)

Not sure mate but my tank was up at 250ppm TDS when dosing EI macros and micros and that was after a few large water changes.  I do have bogwood and some fossilised wood but I don't imagine they would contribute much to conductivity.  TDS maybe but the are not really one and the same. if you evaporated everything out of solution and weighed the remaining solids I believe that would be a truer TDS measurement but there are some contributors to TDS that are not in ionic form and this cannot be measured with a conductivity (TDS) meter.


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## sciencefiction (8 Feb 2017)

AverageWhiteBloke said:


> Surely other things like hard scape will make a difference.



They probably can but its your choice whether to use such hardscape. Your tank water is simply not soft anymore and doing a water change with TDS of just 18 is possibly stressing the critters unless its extremely small.


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## AverageWhiteBloke (8 Feb 2017)

sciencefiction said:


> They probably can but its your choice whether to use such hardscape. Your tank water is simply not soft any more and doing a water change with TDS of just 18 is possibly stressing the critters unless its extremely small.



I deliberately used the Seiryu stone in my scape because of its hardening qualities. As I said my tap water is pretty much devoid of any minerals so it helps to buffer it up a bit. I change 50% water weekly in a 100 ltr tank and dissolve 1tsp epsom salts to each 25ltr bucket prior to it going into the tank giving me the recommended weekly 10ppm magnesium as well as taking my time with the change wherever possible. I also add my KNP salts at the same time so the difference to the fish is minimal.

I've no doubt there is a build up in my tank of most things but every now and again I realise I forgot to dose and just don't worry about it.


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## sciencefiction (8 Feb 2017)

It defeats the point of having soft water. My TDS is 270-ish ppm straight out of the tap and that's considered hard water. Unless you're keeping fish that like that sort of TDS, I'd reset the tank via water changes, take the stones out and find a better way of raising the TDS to a much lower level than the current 250.


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## AverageWhiteBloke (8 Feb 2017)

It's no worry really. I keep fish that are comfortable at those parameters and the stone only raises the KH by about half a degree weekly. It's probably more a build up of other things than the actual stone. 
That's on a week by week basis with normal dosing and 50% weekly changes. When I do a filter change normally around four to six weeks I change around 70% of the water which gives my reset. Sometimes I even throw an extra change in mid week if I have the time. 250ppm is sort of my upper limit just before WC.  Generally it will be lower. 
My tank is nearly fully stocked right now. Only have half a dozen pygmy Cory's to get, once these go in I'm going to start reducing the Ei dosing gradually to see what I can get away with so this should also reduce the speed the tds rises. 

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