# TDS getting lower



## Big G (24 Dec 2020)

Hope everyone is having a good Christmas eve 🙂

Curious to know which of these, if any, might account for a TDS lowering;

(Water fresh from tap with conditioner = 310, tank , which is low energy planted,currently  showing 240).

Dodgy TDS meter

Plants absorbing mineral components faster and disguarding waste slower than top ups and water changes (suggesting I need mote frequent or perhaps larger changes)

A batch of lower TDS tap water that I didn't test coming into the tank.

Some of the botanicals, dried leaves or powdered bio-builders and shrimp baby supplements I use absorbing minerals.

Some sort of ion exchange or cation effect from hardscape, substrate or the above.

Fluctuating temperature (within 2-3c in this tank which has a mean average of 22c)

Something else?

It's a mystery to me at the moment.

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## dino21 (24 Dec 2020)

Hi,
What is your water conditioner ? and what is your tap water TDS before you add the conditioner ?
Could it be that when introduced to the tank the condtioner is still active and able to bind up things that could affect your tanks TDS.
Have you any livestock in the tank  which normally increase the TDS ?


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## Big G (24 Dec 2020)

dino21 said:


> Hi,
> What is your water conditioner ? and what is your tap water TDS before you add the conditioner ?
> Could it be that when introduced to the tank the condtioner is still active and able to bind up things that could affect your tanks TDS.
> Have you any livestock in the tank  which normally increase the TDS ?


That's an excellent thought. Thank you.
I'll run some tests on non-conditioned tap water, freshly conditioned and matured conditioned after say a few days to a week.

Nerites and colony of Neocaradina. Maybe drawing in stuff for chitin development etc?

Expect it would be very marginal but it's a small tank, perhaps combined with affects of a recent shift to smaller water changes. Don't know if would impact DOC rate too and if that would affect TDS. Might explain some of the older leaf degeneration. I've felt less need to syphon as much everything appeared to be pretty balanced.
I have a small but persistant green hair algae issue. Maybe that's pulling in minerals, even faster than the plants?

DW's Frogbit index suggests ferts are sufficient.

In the short run think I'll do a couple of 20% trickle WC's  just in case the expected rise in TSD shocks the shrimp, take TSD after each and rig the test samples.

Cheers

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## dw1305 (24 Dec 2020)

Hi all, 


Big G said:


> A batch of lower TDS tap water that I didn't test coming into the tank.


Most likely that one. Unless you get all your tap supply from a <"deep underground limestone aquifer"> you will get seasonal variation, higher TDS in the summer and lower in the winter when you have the dilution effect of rainwater on shallow aquifers, rivers and reservoirs.


Big G said:


> Nerites and colony of Neocaradina. Maybe drawing in stuff for chitin development etc?





Big G said:


> Plants absorbing mineral components faster and disguarding waste slower than top ups and water changes


Possibly those as well. I wouldn't worry. 


Big G said:


> Don't know if would impact DOC rate too and if that would affect TDS.


It would, but the TDS meter <"doesn't measure TDS">, it  measure electrical conductivity (basically the ions in solution) and then uses a conversion factor to estimate the ppm TDS.

cheers Darrel


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## Big G (24 Dec 2020)

As always, thank you for that Darrel.

So much to learn and understand but it's just starting to gel a bit. So much more to understand. Will need to learn more about TDS/Ionic exchange, for example.

Yes, we looked at the water report for this area a while back and you put up a very helpful cross-section of the underlying rock strata that shape this part of the world. Makes a lot of sense it's different at times. Water supplier is only legally obliged to keep it below about 500 and above 100 I believe. 
Fair enough.

Best wishes and thanks
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## dw1305 (24 Dec 2020)

Hi all, 


Big G said:


> Yes, we looked at the water report for this area a while back and you put up a very helpful cross-section of the underlying rock strata that shape this part of the world.


It is pretty easy for most of S. England, I live just East of  Bath (Jurassic age limestones), and from Corsham you  can see the westernmost edge of the Cretaceous chalk to the South (Salisbury Plain) and East of us (Pewsey Downs). <"That layer of chalk"> spreads all across S England, up the E. Coast to Yorkshire and under the N. Sea to Germany and South of the English Channel across N. France into Champagne etc. 

In that whole huge region nearly all the aquifers are in the chalk and the water is hard and fully saturated with calcium carbonate (CaCO3). In some cases the chalk is overlain by impervious deposits, but in most cases you can't build reservoirs and all the water comes from springs and aquifers.





By Woudloper - Own work, CC BY-SA 3.0, File:Geologic map SE England & Channel EN.svg - Wikimedia Commons

cheers Darrel


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## sparkyweasel (24 Dec 2020)

Big G said:


> Some sort of ion exchange or cation effect from hardscape, substrate or the above.


What substrate are you using?


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## Big G (24 Dec 2020)

sparkyweasel said:


> What substrate are you using?


Tropica aquasoil - the smaller granule version. Sand area in the middle. Unipak silver sand. Sort of shallow egg crate under most of the rockwork.  I opened a small channel in many of the grid edges to allow some movement and bypass.

Merry christmas 👍

Big G


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## sparkyweasel (24 Dec 2020)

That's an active substrate, appears to remove hardness and possibly other things. There's some discussion about it here;
Aquasoil

Merry Christmas.


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