Help with TDS

X3NiTH

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Joined
13 Apr 2014
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944
Thanks all for the above.

That was an interesting water change.

After water change - 228 TDS

After Prime, Excel, 2 tsp of K2SO4 (and yes this made my PH drop from 6.8 to 6.2 as normal - who knows why), 4 tsp of Epsom Salts, and 2 tsp of Gypsom - 515 TDS (also been hanging 2 small bags of crushed coral over the side of the tank for 30 minutes - I take it out after 20 hrs).

I'll add some KNO3 and KH2PO4 in the morning and no doubt be back up to where I started.
Yep that lot would do it!

:)
 

dw1305

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7 Apr 2008
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nr Bath
Hi all,
At pH=6.5, for example, approx. 50% of the DIC* is in the form of bicarbonate so doesn't that mean the other 50% is hydrogen ions?
No, the vast majority of CO2 remains in solution as a dissolved gas, a very small proportion of it (0.15%) becomes carbonic acid (H2CO3) which disassociates into a H+ (proton) and HCO3- ion.

Acids are "proton donors", you've added a proton H+ and the pH falls.

cheers Darrel
 

dw1305

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nr Bath
Hi all,
Many thanks for your reply immediately above.
I knew "acid rain" was a problem, but I must admit before I joined this forum I'd always assumed that all the CO2 went into solution as carbonic acid, I didn't realise that most of it remained as dissolved gas.

cheers Darrel
 

JoshP12

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Joined
8 Dec 2019
Messages
281
Location
Canada
Thanks all for the above.

That was an interesting water change.

After water change - 228 TDS

After Prime, Excel, 2 tsp of K2SO4 (and yes this made my PH drop from 6.8 to 6.2 as normal - who knows why), 4 tsp of Epsom Salts, and 2 tsp of Gypsom - 515 TDS (also been hanging 2 small bags of crushed coral over the side of the tank for 30 minutes - I take it out after 20 hrs).

I'll add some KNO3 and KH2PO4 in the morning and no doubt be back up to where I started.
I’d test that TDS again right now! Sometimes Prime makes it spike while it is working - then it goes down.

The other day, I added prime and tested TDS, went upstairs got a drink to ponder, came back down and it lowered.

I suspect it has to do with the dechlorination process.

Josh
 

jaypeecee

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Joined
21 Jan 2015
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1,207
Location
Bracknell
Hi @dw1305
I knew "acid rain" was a problem, but I must admit before I joined this forum I'd always assumed that all the CO2 went into solution as carbonic acid, I didn't realise that most of it remained as dissolved gas.
I can't quite get my head around this. I think I'm having difficulty with the expression 'dissolved gas'. I guess it may be appropriate to think of carbonated drinks. Perhaps the CO2 is distributed throughout the liquid as microscopic bubbles (injected under pressure). When the cap is taken off the bottle, the pressure drops and the bubbles come to the surface of the drink. So, how does this relate to injected CO2 in our tanks, if at all? If we magnified a volume of tank water, would we see ultra-small CO2 bubbles moving around? If that is the case, then they're not really dissolved, are they?

I seem to recall that Clive (ceg4048) once talked about dissolved sugar cubes in a cup of tea but I haven't a clue where it was.

JPC
 
Last edited:

Nick72

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Joined
21 Apr 2020
Messages
169
Location
Kuala Lumpur, Malaysia
I’d test that TDS again right now! Sometimes Prime makes it spike while it is working - then it goes down.

The other day, I added prime and tested TDS, went upstairs got a drink to ponder, came back down and it lowered.

I suspect it has to do with the dechlorination process.

Josh

Hi Josh, just recheck 518 TDS so no real change.
 

jaypeecee

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21 Jan 2015
Messages
1,207
Location
Bracknell
Hi @Nick72

I apologize for unintentionally steering your thread off-course with the CO2 finer detail. I'd like to pursue this further with @dw1305 so I suspect that the best way for me to do this is via PM.

JPC
 
Joined
3 Jan 2016
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315
Location
Woking, UK
I can't quite get my head around this. I think I'm having difficulty with the expression 'dissolved gas'. I guess it may be appropriate to think of carbonated drinks. Perhaps the CO2 is distributed throughout the liquid as microscopic bubbles (injected under pressure). When the cap is taken off the bottle, the pressure drops and the bubbles come to the surface of the drink. So, how does this relate to injected CO2 in our tanks, if at all? If we magnified a volume of tank water, would we see ultra-small CO2 bubbles moving around? If that is the case, then they're not really dissolved, are they?
No, if you were to dissolve some CO₂ in water and then observe with a powerful enough microscope, you wouldn’t see any bubbles. If it were possible to zoom in further, you’d eventually see CO₂ molecules roaming the spaces between the H₂O molecules. There would be some electrostatic interaction between CO₂ molecules and the water molecules, which I believe is what makes it possible for the CO₂ to dissolve.

When a fizzy drink is kept under pressure, that pressure is what’s preventing the CO₂ leaving the liquid solution and becoming gas. I’m unsure of the small-scale reason for that, but it may help to imagine the CO₂ molecules hiding in the gaps between water molecules because that’s how they can occupy less volume. As soon as you release the pressure, it becomes easier for the CO₂ molecules to exit the water, and so they come out of solution and form gas bubbles. In a sense, dissolved CO₂ isn’t really a gas.
 

Jonatk

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7 Jan 2018
Messages
29
Location
Tyneside
Hi, How much of a water change do you do? I had a similar problem last year. I have a 120x 60 x60cm tank with medium density planting. I was only doing 25% water changes and i found my TDS climbed to similar levels as yours. I sort some advice from the forum and after doing a series of water changes 24hrs apart that brought the levels right down. I then switched to 50% weekly water changes and have had no problems since.
 

Nick72

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21 Apr 2020
Messages
169
Location
Kuala Lumpur, Malaysia
Hi, How much of a water change do you do? I had a similar problem last year. I have a 120x 60 x60cm tank with medium density planting. I was only doing 25% water changes and i found my TDS climbed to similar levels as yours. I sort some advice from the forum and after doing a series of water changes 24hrs apart that brought the levels right down. I then switched to 50% weekly water changes and have had no problems since.
I do 60% -80% water changes once a week. Always have.

When I add up each of the Salts I use for EI dosing and GH + KH buffer it is around 200ppm per week.

Then add some Prime, daily Excel, and a some organics from the plants, then it's no surprise that the TDS can reach these levels.

I'm not concerned now I understand where the ppm are coming from. It's all additives that I want in the tank, and no one above has given any reason why this should be an issue.
 

Jonatk

Member
Joined
7 Jan 2018
Messages
29
Location
Tyneside
I do 60% -80% water changes once a week. Always have.

When I add up each of the Salts I use for EI dosing and GH + KH buffer it is around 200ppm per week.

Then add some Prime, daily Excel, and a some organics from the plants, then it's no surprise that the TDS can reach these levels.

I'm not concerned now I understand where the ppm are coming from. It's all additives that I want in the tank, and no one above has given any reason why this should be an issue.
I too was chasing GH and KH numbers around by adding various products to my tank. My GH and KH figures were the same as yours. I now only add crushed oyster shell to the external filter to buffer the ph, Excel and my E.I dosing. I have gouramie, tetra, corys, hatchetfish etc. I find that the fish are happy with the water parameters and plants are growing great. Why not leave it another 24hrs and do a water change, then leave it another 24hrs and do another, but without adding everything else. Then see where your tds is.
 

Nick72

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Joined
21 Apr 2020
Messages
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Location
Kuala Lumpur, Malaysia
I too was chasing GH and KH numbers around by adding various products to my tank. My GH and KH figures were the same as yours. I now only add crushed oyster shell to the external filter to buffer the ph, Excel and my E.I dosing. I have gouramie, tetra, corys, hatchetfish etc. I find that the fish are happy with the water parameters and plants are growing great. Why not leave it another 24hrs and do a water change, then leave it another 24hrs and do another, but without adding everything else. Then see where your tds is.
Why?

What is the issue with a TDS of 542?

My fish are all extremely happy and healthy, my plants are now growing well, where as I struggled to grow anything before increasing the GH.

So far no one has said a TDS of 500+ is bad because?

Or you should avoid a TDS of over 300 because?

So why are you advising me to lower my TDS?
 
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