# Perplexed about extreme TDS readings



## MichaelJ (13 Mar 2021)

This is my first post here (Hi!).. and hope I am posting to the right thread.

My TDS in both my heavily planted 40g tanks are in the 1500 ppm range, and I do not understand why it is so high.

My general readings for both tanks:
KH 6-7
GH 8-9
Ph 6.8 - 7.0
Nitrate levels around 20 ppm.
Nitrite and ammonia ~ 0 (untraceable)
Phosphate 5-10 ppm
Not adding CO2.

Both tanks are about 8 months old.


I fertilize with Tropica Premier (14 ml - or 6 pumps) once a week after 20% WC and 5 ml Seachem Trace and 5ml  Flourish Comprehensive mid week. Thats it. Most of my plants are doing really well. My 20% WC is mineralized RO water. The TDS is about 2-3 ppm when pure and about 280 ppm after mineralization using Seachem Adic buffer,  Alkaline and Equilibrium.

I did think my TDS meter was at fault, but with a solution of 1 liter RO water and 0.5 gram of table salt the TDS comes out around 550 ppm. 1 gram of salt in 1 liter of RO water around 1200 ppm, so I am assuming the 1500 ppm readings in the tanks are probably a fairly good indicator that the TDS is on the extreme end.

Other than plants I only I have drift wood. The substrate in both tanks are CaribSea Eco-Complete (Red) planted tank substrate which _should be_ inert. As plants and fish (tetras, Rams and angels) are doing great, I am really mostly curious rather than worried about it.

Cheers,
Michael


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## ceg4048 (14 Mar 2021)

Hello,
        Assuming your probe reads accurately, the next suspect could be your acid buffer (which you really don't need). Acid buffers used to be made from highly toxic phosphoric acid, but the marketing on that product seem to imply that it is not H3PO4. It claims to convert Carbonate and/or bicarbonate to CO2 and the mot obvious agent would be Carbonic acid, a favorite of cola and other fizzy drink bottlers.
It could be that the acid is dissolving something in the tank i.e. something containing chalk or limestone so that the residue shows up as TDS. Try not using any of the buffers and just remineralize with Equilibrium.

The next suspect, of course, would be the plants themselves, which can dump large amounts of carbohydrates into the water, which again shows up as TDS. This usually happens in CO2 injected tanks and would be unusual in non-CO2 tanks like yours.

Cheers,


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## MichaelJ (14 Mar 2021)

Thanks for the helpful insights. 
So the Seachem Alkaline Buffer I use to (raise) target the 6-7 KH range (for Ph buffering). However, since that raises the Ph of the RO water from 7 to around 8.5, I am adding the Acid Buffer to bring the Ph back down to the neutral range. I am trying to make the RO water (with respect to Ph, KH and GH) close to identical to that of the tank water. Perhaps thats a misconception?
I am not a big fan of adding all those abrasive chemicals anyway, so if there is a way I can just raise the KH without raising the Ph then it should be fine I suppose. Otherwise, if I don’t add the Alkaline Buffer my KH would slowly wind down with each WC and eventually become too low (after about five  20% WC’s). Or, if I only add Alkaline and Equilibrium my Ph would drift upwards and eventually be too high for the fish.

I will try only Equilibrium for a couple of WC’s to see how how that works out.

Another thing I was wondering about is plant decay. In a heavily planted tank its sort of hard to get in-between the plants and clean up. I think I am doing an okay job, but there are always spots I cant get to without messing things up. Perhaps that a contributing factor to the extreme TDS as well.

Thanks!
Michael


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## jaypeecee (14 Mar 2021)

MichaelJ said:


> The substrate in both tanks are CaribSea Eco-Complete (Red) planted tank substrate which _should be_ inert.


Hi @MichaelJ 

I am unable to determine if _CaribSea Eco-Complete (Red)_ has the same composition as _Caribsea Eco-Complete (Black)_. But, I suspect they are essentially the same - apart from colour. If that is indeed the case, then I think the answer to your question lies with this description:

"Contains Iron, Calcium, Magnesium, Potassium, Sulfer plus over 25 other elements to nourish your aquatic plants.

Eco-Complete Planted Aquarium Substrate contains all the mineral nutrients needed for luxuriant aquatic plant growth without nuisance algae!"

It's certainly not inert!

JPC


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## jaypeecee (14 Mar 2021)

Hi again, @MichaelJ 

One important thing that I forgot...

Welcome to UKAPS!

JPC


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## dw1305 (14 Mar 2021)

Hi all,
Welcome Michael,
I'm sorry that the links in this contains so much chemistry, but it all takes a bit of unravelling.


MichaelJ said:


> so if there is a way I can just raise the KH without raising the Ph then it should be fine I suppose.


Not really, pH in carbonate buffered water (water with some dKH) will always end up about pH8, because of the <"CO2~carbonate equilibrium">. If you add more dKH (an H+ acceptor) then you need more acid (a H+ donor) to convert that HCO3- to CO2.

The pH value is dependent upon <"the level of CO2 in the atmosphere"> (about 415 ppm CO2). It is the dKH ~ CO2 relationship that we use in a <"drop checker">


MichaelJ said:


> So the Seachem Alkaline Buffer I use to (raise) target the 6-7 KH range (for Ph buffering). However, since that raises the Ph of the RO water from 7 to around 8.5, I am adding the Acid Buffer to bring the Ph back down to the neutral range. I am trying to make the RO water (with respect to Ph, KH and GH) close to identical to that of the tank water. Perhaps thats a misconception?


Yes, it is a misconception, with the buffers you are <"_giving with one hand and taking with the other_">. The sellers of "pH buffers" are, at best, disingenuous about what their products do, and their <"advertising implies all sorts of things">, without ever making a statement that is provably false.


MichaelJ said:


> ........ and about 280 ppm after mineralization using Seachem Adic buffer, Alkaline and Equilibrium.


I wouldn't add anything to raise dKH or dGH before you add your fertilisers. If you want to add a <"little bit dGH and dKH"> you can use a DIY mix, details are at <"James' Planted Tank">. If your tap water is hard? <"you can just add a bit of that">.

I don't actually worry too much about pH, because as you approach pure H2O (like your RO) pH becomes of <"very limited value">. This is because pH is both a ratio and a log10 value. I tend not to worry too much about pH in soft water, because it can never be stable and small changes in water chemistry cause large changes in pH.


MichaelJ said:


> My TDS in both my heavily planted 40g tanks are in the 1500 ppm range, and I do not understand why it is so high.





MichaelJ said:


> I did think my TDS meter was at fault, but with a solution of 1 liter RO water and 0.5 gram of table salt the TDS comes out around 550 ppm. 1 gram of salt in 1 liter of RO water around 1200 ppm, so I am assuming the 1500 ppm readings in the tanks are probably a fairly good indicator that the TDS is on the extreme end.


Looks like that is a genuine value (but as <"electrical conductivity microS, rather than ppm TDS)">, you've checked against a standard, if any-one is interested the <"working are here">.

My simple answer would be just add less fertilisers until the number comes down. I use a <"conductivity datum range"> and plant health, rather than adding nutrients regularly.

cheers Darrel


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## Wookii (14 Mar 2021)

This is a strange one - something is definitely off with the numbers somewhere.

As Clive says you don’t need to add the Acid buffer. All it’s doing to removing the carbonates you are adding with the Alkaline buffer. Just add enough alkaline buffer to target 1-2dKH, and the Equilibrium for GH, and don’t use the acid buffer.

It could be that the acids you are adding in the buffer are reacting with the Eco Complete - though I would have thought there’d be more reports of high TDS in CO2 injected tanks with this substrate if that were the case.

Either way 1500ppm is extremely high if you are using RO (and even if you weren’t).

The only other thing I can think is something is throwing off your TDS meter. Have you tried taking the TDS measurement in a glass of tank water, rather than directly in tank?


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## Wookii (14 Mar 2021)

dw1305 said:


> My simple answer would be just add less fertilisers until the number comes down. I use a <"conductivity datum range"> and plant health, rather than adding nutrients regularly.
> 
> cheers Darrel



Surely you’d have to add an insane amount of ferts to cause a 1200ppm increase in TDS though Darrel? I once accidentally triple dosed EI level ferts, and it only added about 100ppm (from memory).


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## jaypeecee (14 Mar 2021)

MichaelJ said:


> I did think my TDS meter was at fault, but with a solution of 1 liter RO water and 0.5 gram of table salt the TDS comes out around 550 ppm.


Hi @MichaelJ 

I didn't comment on your statement above but I would expect a TDS figure around 500 ppm with the solution you made up. This tallies well with your measurement so I think you can safely say that your TDS meter is giving you a correct reading.

JPC


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## dw1305 (14 Mar 2021)

Hi all, 


Wookii said:


> Surely you’d have to add an insane amount of ferts to cause a 1200ppm increase in TDS though Darrel?


My guess is that the levels have built up over the 8 months, probably mainly from the excess calcium (Ca++), sodium (Na+), chloride (Cl-) etc the ions that plants don't require or only require in small amounts.

cheers Darrel


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## jaypeecee (14 Mar 2021)

Hi Guys,

Surely, the answer lies with the substrate, doesn't it? It's awash with fertilizers, isn't it?

JPC


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## Siege (14 Mar 2021)

Easy -

Do a 80% water change whilst cleanping the substrate and everything else. Do another 80% water change.

Next week clean and 75%, weeks thereafter repeat!

Happy days 👍😃


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## dw1305 (14 Mar 2021)

Hi all,


jaypeecee said:


> Surely, the answer lies with the substrate, doesn't it? It's awash with fertilizers, isn't it?


I expect some of it is, but the plants will mop that up and it has been eight months? I've never used any nutrient rich substrates, so I don't have any practical experience of them.


Siege said:


> Do a 80% water change, clean the substrate and everything else. Do another 80% water change.
> 
> Next week clean and 75%, weeks thereafter repeat!


That one.

cheers Darrel


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## jaypeecee (14 Mar 2021)

dw1305 said:


> I expect some of it is, but the plants will mop that up and it has been eight months?


Hi Darrel (@dw1305)

One thing we don't know is the _depth_ of the substrate. If it's, say, 10cm depth, it could take a long time for all the ferts to leach out of it/be taken up by the plants, don't you think? As for how long, well, how long's a piece of string?

JPC


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## Wookii (14 Mar 2021)

jaypeecee said:


> Hi Darrel (@dw1305)
> 
> One thing we don't know is the _depth_ of the substrate. If it's, say, 10cm depth, it could take a long time for all the ferts to leach out of it/be taken up by the plants, don't you think? As for how long, well, how long's a piece of string?
> 
> JPC



As far as I understand it from Tom
Barrs comments on Eco Complete, it’s largely inert rock, and has very little in the way of ferts or CEC compared to, say, aquatic soils, or whatever their marketing department would like people to believe.


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## jaypeecee (14 Mar 2021)

jaypeecee said:


> "Contains Iron, Calcium, Magnesium, Potassium, Sulfer plus over 25 other elements to nourish your aquatic plants.
> 
> Eco-Complete Planted Aquarium Substrate contains all the mineral nutrients needed for luxuriant aquatic plant growth without nuisance algae!"



Hi Guys,

So, does that mean the above isn't worth the computer screen it's written on? I guess we'll never know. I wait, with interest, to hear what the OP's comments are. Until then...

JPC


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## MichaelJ (15 Mar 2021)

I really appreciate the feedback and welcome greetings. Thank you!

I am learning a lot here already.

So, in no particular order:

My impression is that the ECO-Complete substrate itself is inert, but the bag (the water or additives in the bag I supposed) contains a number of minerals and nutritions to get the initial growth started. But after 8 months I would expect the effect of that would be gone?   

As for substrate depth, I would say both tanks got about a layer of about 3.5 inches (about 9 cm) - less in the front, and more towards the back.

I guess one way of figuring out the inertness of the gravel is to dig some up and let it sit in a bucket of RO water and see what happens to the TDS after a couple of days or a week perhaps?

I am definitely going with the recommendation of stop using the Acid and Alkaline Buffers and see what happens.

If its a buildup of sodium, chloride or calcium ( wouldn’t a huge buildup of Ca give me a very high GH reading?) or maybe potassium, then I suppose I just need to do some very large WCs, and perhaps do a bit less fertilizer from now on as suggested.

Another thing, I am filtering over Seachem Purigen and Matrix. I don't think that factors in, but just wanted to add that in case anyone was wondering.

Cheers,
Michael


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## MichaelJ (15 Mar 2021)

Wookii said:


> The only other thing I can think is something is throwing off your TDS meter. Have you tried taking the TDS measurement in a glass of tank water, rather than directly in tanJust k?


Just tried this in one of the tanks. The TDS in a glass of tank water is 1563 and 1558 in the tank...   I tested the TDS meter with a solution of 1 liter of RO water and 0.5 and 1 gram of table salt and it pretty much matches the expected values. I am getting around 550 and around 1200 ppm respectively. Close enough I would say  (I suppose the meter, my scale, liter measure and water temperature, which ideally should be 25C for the meter, might be off by a bit, but the numbers seems fairly well in the ballpark for me to trust that the meter is not being too much off from what I except it to be... I probably wouldn't trust it for anything below +/- 50 ppm).


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## dw1305 (15 Mar 2021)

Hi all,


MichaelJ said:


> If its a buildup of sodium, chloride or calcium ( wouldn’t a huge buildup of Ca give me a very high GH reading?)


Yes, if you had more calcium (Ca++) in your water it should show up on the dGH test. You will never get a huge build up of Ca++ ions, purely because of <"the limited solubility"> of most calcium containing compounds. Water is fully saturated with Ca++ and HCO3- at about 17 dGH/dKH, which is somewhere near 600 microS.

I don't know exactly how the dGH test kit works, I tend to use conductivity as a proxy for dissolved CaCO3 in natural waters, and it is easy to test for in the lab. with <"ICP, AAS or flame photometry">. 

In practical terms all potassium (K), sodium (Na) and chloride (Cl-) salts are soluble.


MichaelJ said:


> then I suppose I just need to do some very large WCs, and perhaps do a bit less fertilizer from now on as suggested.


That would be my suggestion. As you've found out, from your meter checks, it isn't a huge addition of salts to raise the conductivity appreciably.

cheers Darrel


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## jaypeecee (15 Mar 2021)

MichaelJ said:


> My impression is that the ECO-Complete substrate itself is inert, but the bag (the water or additives in the bag I supposed) contains a number of minerals and nutritions to get the initial growth started.


Hi @MichaelJ 

So, if I understand you rightly, there are two things in a bag of _Eco Complete_ - the sand/gravel itself and a solution of nutrients. Is that correct? Is it a (small amount of) solution or is there evidence of solids (as powder or crystals) mixed into the inert substrate material? Does it contain organic matter?

JPC


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## jaypeecee (15 Mar 2021)

Hi @MichaelJ 

Looks like you're not alone with _Eco Complete_ problems:









						Carib sea eco complete problems | Freshwater Substrates - Gravel, Sand Forum | 436267
					

I posted in cloudy water but I thought I would post here too to see if anyone else had the same issues I did or can offer insight. I redid my 29 gallon with carib sea eco complete (about 3-4" )  Same bio media in filter that has been going for years.  No fish to start(switched to my other tank)...




					www.fishlore.com
				




JPC


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## MichaelJ (15 Mar 2021)

jaypeecee said:


> Hi @MichaelJ
> 
> Looks like you're not alone with _Eco Complete_ problems:
> 
> ...



Hi JPC,

I do not know the exact content of the ECO Complete substrate. I've added some screen shots of the text from the Red EcoComplete planted aquarium substrate bag that gives more details about what CaribSea claims is the contents. It was recommended to me back in the day. However, there is really nothing from what it says on the bags that suggest it is completely inert I suppose?

I never had issues (to my knowledge) with sick/dying fish or elevated nitrate or ammonia levels since using this substrate. That being said, I do suspect the gravel is playing into my super elevated TDS levels somehow - perhaps worsened in part due to my past use of the Acid buffers as pointed out in the this thread. I am having a cup full of the gravel from the tank sitting in a bucket of RO water for a couple of days and see what happens to the TDS. Of course, that experiment won't tell me anything if its interaction between my current tank water and the substrate.

Cheers,
Michael


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## jaypeecee (15 Mar 2021)

Hi @MichaelJ 

The sequence of events/key facts appear to be:



MichaelJ said:


> The TDS is about 2-3 ppm when pure and about 280 ppm after mineralization using Seachem Adic buffer, Alkaline and Equilibrium.



And then:



MichaelJ said:


> So the Seachem Alkaline Buffer I use to (raise) target the 6-7 KH range (for Ph buffering). However, since that raises the Ph of the RO water from 7 to around 8.5, I am adding the Acid Buffer to bring the Ph back down to the neutral range.



And then:



MichaelJ said:


> My TDS in both my heavily planted 40g tanks are in the 1500 ppm range...



So, it is a combination of factors that has driven TDS so high. Last night, I was having some difficulty getting the full picture. Looking at the list of ingredients in _Eco Complete_, the manufacturers really have tried to pack everything in there. It contains mycorrhizal fungus and even strains of probiotics.

JPC


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## jaypeecee (15 Mar 2021)

MichaelJ said:


> As plants and fish (tetras, Rams and angels) are doing great, I am really mostly curious rather than worried about it.


Hi @MichaelJ 

Isn't it astonishing that your fish have been OK in this water? Out of interest, what has been your recent GH and KH in this tank?

JPC


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## MichaelJ (15 Mar 2021)

Hi JPC,

My most recent KH are 6-7 and GH 8-9.  Although I am not hyper confident with these cheap drop-counting test kits, I do expect them to be at least accurate within say +/- 1 KH and +/- 1 GH. (based on my experience when preparing RO water and measuring). So I suppose the tanks could be in the KH 5-8 range and GH 7-10 range.

To be honest, I am rather clueless about what the TDS limits are for my specific plants and my specific fish. I suppose it depends a lot on what makes up the TDS in the first place.  Both plants and fish seems to be doing good since I started to pay attention to the high TDS a couple of months ago.

Cheers,
Michael


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## sparkyweasel (15 Mar 2021)

jaypeecee said:


> "Contains Iron, Calcium, Magnesium, Potassium, Sulfer plus over 25 other elements to nourish your aquatic plants.


If that includes the 17 elements necessary for plants (maybe 14 as C, H and O are available from the water and its dissolved air) I wonder what the other 13+ (or 16+) are for?


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## jaypeecee (15 Mar 2021)

Hi @MichaelJ

Some time ago, I empirically determined a numerical relationship between KH, GH and TDS. It is this:

(dKH + dGH) x 18 is approximately equal to TDS (in ppm) if we're talking about freshly-buffered RO/DI water. Unless I'm overlooking something, this should hold true if we're considering carbonate and bicarbonate (as anions) + calcium and magnesium (as cations). Therefore, with your current KH and GH figures, this would approximate to 270 ppm TDS. Anything more than that is the result of all the other ions in your tank water.

Feel free to point out any errors in my reasoning. My professional background is in physics, not chemistry. That's my excuse, anyway!

JPC


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## sparkyweasel (15 Mar 2021)

jaypeecee said:


> Surely, the answer lies with the substrate, doesn't it?


That would be my prime suspect too. Apparently it contains lots of things, but we don't know what they all are, how quickly it releases them, or what factors affect the rate of release.


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## sparkyweasel (15 Mar 2021)

dw1305 said:


> I don't know exactly how the dGH test kit works,


Neither do I, but I wonder if acid and alkaline buffers would interfere with its reaction.
I will try to find out. I used to know exactly who to ask, but he is no longer with us.


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## sparkyweasel (15 Mar 2021)

And, Welcome! to @MichaelJ


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## MirandaB (15 Mar 2021)

I've used Eco complete for quite a few years in my Crypt dominated tanks as they seem to grow very well in it but I've never come across an issue like this.
In appearance it's like crushed lava rock although it does have smaller slightly crystalline particles but I don't know if that's just dust from the milling process.


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## MichaelJ (15 Mar 2021)

HI JPC,


jaypeecee said:


> Hi @MichaelJ
> 
> Some time ago, I empirically determined a numerical relationship between KH, GH and TDS. It is this:
> 
> ...



Yes, your (dKH + dGH) x 18 = TDS for freshly buffered RO water seems like a good approximation to me. As as matter of fact, I am reading about 280-300 ppm TDS with my prepared RO water (targeting KH 6-7 and 8-9 GH). Whatever is making up the majority of the of additional 1200 ppm in the tanks is the mystery I suppose. If it would be something that is toxic in large quantities I suppose especially the fish would have shown signs of that by now.


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## MichaelJ (15 Mar 2021)

sparkyweasel said:


> And, Welcome! to @MichaelJ


Thank you!


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## MichaelJ (15 Mar 2021)

MirandaB said:


> I've used Eco complete for quite a few years in my Crypt dominated tanks as they seem to grow very well in it but I've never come across an issue like this.
> In appearance it's like crushed lava rock although it does have smaller slightly crystalline particles but I don't know if that's just dust from the milling process.


My Crypts are doing really well too...  Yes, they do mention "volcanic grains" on the bag.


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## MirandaB (15 Mar 2021)

It's a shame they don't do the smaller grain size anymore but apparently the cost of milling it finer was too much.


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## jaypeecee (15 Mar 2021)

MichaelJ said:


> If it would be something that is toxic in large quantities I suppose especially the fish would have shown signs of that by now.


I don't think there can be much doubt about that.

JPC


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## Maf 2500 (15 Mar 2021)

The screenshot of the back of the bag says in small print at the bottom:


> Eco complete may elevate pH above neutral and may not be suitable for Discus sp., P. alta and sensitive freshwater shrimp.


While the statement sounds like corporate ass-covering it does introduce the idea that it can release _something _into the water column and has the possibility to affect water chemistry. It is out of my experience area how this would interact with the acid and alkaline buffers that have been added to the water.


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## MichaelJ (15 Mar 2021)

Maf 2500 said:


> The screenshot of the back of the bag says in small print at the bottom:
> Eco complete may elevate pH above neutral and may not be suitable for Discus sp., P. alta and sensitive freshwater shrimp.
> While the statement sounds like corporate ass-covering it does introduce the idea that it can release _something _into the water column and has the possibility to affect water chemistry. It is out of my experience area how this would interact with the acid and alkaline buffers that have been added to the water.


Yes, for sure. I never experienced any elevated Ph, KH or GH from this substrate though... or at least nothing my weekly 20% WC wouldn't smooth out. But who knows what else it might be releasing.

I will have to research if I could find a lab somewhere around here that could take a sample of my tank water and analyze it at a decent cost and tell me what makes up the TDS.


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## dw1305 (16 Mar 2021)

Hi all, 


MichaelJ said:


> tank water and analyze it at a decent cost and tell me what makes up the TDS.


A lab. that <"has an ICP-MS"> would be able to do it. There are companies that run samples for marine aquarists.

Personally I wouldn't be too bothered. I'd just add less salts, watch plant health and change more water until the conductivity value comes down to one where you are happy with plant growth. 

If I was a betting man, my money would be on a combination of SO4--, Na+, Cl-, HCO3- and Ca++.

cheers Darrel


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## MichaelJ (16 Mar 2021)

dw1305 said:


> Hi all,
> 
> A lab. that <"has an ICP-MS"> would be able to do it. There are companies that run samples for marine aquarists.
> 
> ...



Yes, especially since whatever is making up this ridiculously high TDS is apparently not hurting (at the moment at least) the fish or the plants, I will just do some extra large WCs over the next couple of weeks (without adding the Acid and Alkaline Buffers to the RO water) and  lower my fertilizer.  I am going to do two weekly 50% WC's and only add the Tropica Premium after the WC's (skipping the midweek Seachem Comprehensive and Trace) and see if that significantly drives down the TDS.

The only thing that worries me a bit is that if I essentially replace 50% with remineralized water with a GH of 8 and a KH of near 0 (as I am not adding the Alkaline Buffers) wouldn't that drive down my current KH of 6-7 to the 1-2 range (and eventually lower with consecutive WCs) where Ph becomes dangerously unstable?    

Cheers,
Michael


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## MichaelJ (16 Mar 2021)

Wookii said:


> This is a strange one - something is definitely off with the numbers somewhere.
> 
> As Clive says you don’t need to add the Acid buffer. All it’s doing to removing the carbonates you are adding with the Alkaline buffer. Just add enough alkaline buffer to target 1-2dKH, and the Equilibrium for GH, and don’t use the acid buffer.



Ok, after re-reading the whole thread. I guess @ceg4048 and @Wookii answered above worries about the KH... I'll just skip the Acid and add enough of the Alkaline Buffer to target 1-2 KH instead of the 6-7 KH I've done in the past. Thanks!

I'll let the thread know how it goes.

Cheers,
Michael


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## dw1305 (16 Mar 2021)

Hi all, 


MichaelJ said:


> The only thing that worries me a bit is that if I essentially replace 50% with remineralized water with a GH of 8 and a KH of near 0 (as I am not adding the Alkaline Buffers) wouldn't that drive down my current KH of 6-7 to the 1-2 range (and eventually lower with consecutive WCs) where Ph becomes dangerously unstable?


Dangerously unstable pH doesn't really occur in very soft water. The pH just <"becomes more variable">.


MichaelJ said:


> the Alkaline Buffer to target 1-2 KH


That is definitely what I'd do (and do). I have hard (about 17 dGH/dKH) good quality tap water and our rainwater has some carbonate buffering. 

cheers Darrel


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## ceg4048 (16 Mar 2021)

MichaelJ said:


> The only thing that worries me a bit is that if I essentially replace 50% with remineralized water with a GH of 8 and a KH of near 0 (as I am not adding the Alkaline Buffers) wouldn't that drive down my current KH of 6-7 to the 1-2 range (and eventually lower with consecutive WCs) where Ph becomes dangerously unstable?


Hello,
        This is yet one more myth that hobbyist should never worry about. pH is just a number and has no meaning by itself and is only relevant within the context of the chemical agents in the water. So the number itself cannot be dangerous unless the number is being driven by a dangerous agent in the water column. This is a concept that many people completely misunderstand. So for example, suppose you were to put battery acid in the water. It would drive the pH very low and would be lethal to the fish, but the fish would not perish as a result of the low pH. They would perish because of the toxic acid. Similarly, suppose you put ammonia in the water. The pH would rise, but the animals would perish due to ammonia toxicity, not due to pH rise.
This is a really important concept because it forces us to look at the reason for the pH reading and to not necessarily be alarmed at the numerical value itself. Since we are not introducing any toxic agents into the tank that coincidentally also have an effect on pH, then there is nothing to worry about. Just like the behavior of your TDS reading, it is not the number itself that is necessarily an issue, for example if it were due to calcium in the water, but if a large portion of the number were due to pollution, i.e. fish waste and uneaten food, then yes it would be a worry because pollution kills, not TDS numerical value.

Cheers,


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## MichaelJ (16 Mar 2021)

ceg4048 said:


> Hello,
> This is yet one more myth that hobbyist should never worry about. pH is just a number and has no meaning by itself and is only relevant within the context of the chemical agents in the water. So the number itself cannot be dangerous unless the number is being driven by a dangerous agent in the water column. This is a concept that many people completely misunderstand. So for example, suppose you were to put battery acid in the water. It would drive the pH very low and would be lethal to the fish, but the fish would not perish as a result of the low pH. They would perish because of the toxic acid. Similarly, suppose you put ammonia in the water. The pH would rise, but the animals would perish due to ammonia toxicity, not due to pH rise.
> This is a really important concept because it forces us to look at the reason for the pH reading and to not necessarily be alarmed at the numerical value itself. Since we are not introducing any toxic agents into the tank that coincidentally also have an effect on pH, then there is nothing to worry about. Just like the behavior of your TDS reading, it is not the number itself that is necessarily an issue, for example if it were due to calcium in the water, but if a large portion of the number were due to pollution, i.e. fish waste and uneaten food, then yes it would be a worry because pollution kills, not TDS numerical value.
> 
> Cheers,


Got it. Numbers don't mean much without context, cause and effect, which essentially is why I didn't worry _too_ much about the high numeric reading of the TDS meter, other that trying to understand the reason, as fish and plants are seemingly doing well. I got the TDS meter for Christmas and probably had the high levels way well before that (both tanks have been running without many issues for about 8 months).

Cheers,
Michael


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