TDS Reading Options

[Tyler LaZerte]

I am reading high TDS (400s) with a TDS meter. I want to make sure it's not incorrect because of the calibration. Is there a way to check TDS without one of the digital TDS meters? Just watched the latest livestream and @Cory said he doesn't like using them so I was curious what the other ways are. 

[Tyler LaZerte]

@Diving Aquarist Okay thank you very much. I know that there aren't horrible things in the water so hopefully it is measuring good solids haha 

[darkG]

Technically TDS is usually too involved to meassure (evaporating water and weighing the small residue) so conductivity is measured instead. TDS can then be estimated by applying a guessed conversion factor. 

Edited May 17, 2021 by darkG

[Cory]

The problem I have with TDS meters is, You could have 100 TDS. It could be hand lotion, nitrates, ammonia, calcium, or dechlorinator. You have no way of knowing. Even two aquariums are different, one has a rotting piece of wood making nitrates. The other has extra dechlorinator in it. The 3rd tank you setup a week ago, has ammonia. And yet they all read 100 TDS leading aquarists to a false sense of security.

[Tyler LaZerte]

Just now, Cory said:

The problem I have with TDS meters is, You could have 100 TDS. It could be hand lotion, nitrates, ammonia, calcium, or dechlorinator. You have no way of knowing. Even two aquariums are different, one has a rotting piece of wood making nitrates. The other has extra dechlorinator in it. The 3rd tank you setup a week ago, has ammonia. And yet they all read 100 TDS leading aquarists to a false sense of security.

I appreciate your feedback, Cory. That's the issue I'm trying to figure out. I just don't know how much I should care about TDS. I've heard people like LRB Aquatics raises award winning Neos in water that has a pH of 8 sand TDS of over 700 and I've heard and known people who say it HAS to be 250 or lower or shrimp won't molt correctly and won't thrive. So I don't know what to think of TDS and how vital it is to anything. 

[Cory]

Here are my thoughts on it.

 

[tonyjuliano]

5 hours ago, Cory said:

The problem I have with TDS meters is, You could have 100 TDS. It could be hand lotion, nitrates, ammonia, calcium, or dechlorinator. You have no way of knowing. Even two aquariums are different, one has a rotting piece of wood making nitrates. The other has extra dechlorinator in it. The 3rd tank you setup a week ago, has ammonia. And yet they all read 100 TDS leading aquarists to a false sense of security.

I agree with Cory.  The main issue with TDS is the numerous variables that contribute to the result.

But...

if you have a good understanding of what it is really all about (and that’s the main problem) then it can be beneficial as a monitoring tool, but only on a “tank by tank” basis.

I have mucho experience with this, a masters degree in wastewater management and a lifetime spent working in the field made that a requirement.

It’s a complicated subject, and I could spend days typing about details, but most of that is beyond the scope of freshwater aquaria necessity.

Here is a LINK to a brief article.  It is well written and explains pretty much everything a serious hobbyist would need (or probably want) to know on the subject.

Using Cory’s example for reference, we can easily measure the “known” variables (chlorine, ammonia, nitrite, nitrate, calcium, potassium, et al), then subtract those from the total, giving an indication (albeit vague) of contamination (it’s that damn hand lotion again!)

It’s also helpful to calculate a “normal” range (based upon the tanks living contents, and their respective desired parameters) to be monitored the same way you would monitor nitrate levels.

It’s just another tool (and a good one if you understand it properly) that can be used to alert you of potential issues as they arise.

Edited May 18, 2021 by tonyjuliano

[CT_]

A slight aside, but my favorite is when a site for how to care for X fish/shrimp lists something like

kh 4-8

gh 5-9

tds <150ppm

4dkh and 5dgh are already 161ppm

Edited May 18, 2021 by CT_

[Andy's Fish Den]

To check your TDS meter, get some RO/DI water. Make sure it is not just reverse osmosis, you need the extra deionization to remove everything from the water and make it pure. Your meter should then read at 0 (zero) When I kept saltwater reef tanks I would check mine all the time because you want your water at 0 before mixing with salt.

[Tyler LaZerte]

@Andy's Fish Den Okay I will try that. Thank you!

[Mmiller2001]

Testing zero in RO/DI as above.
 

And if you have some baking soda around,

.5g of NaCl in 1 gallon of RO\DI water should test 132.09 

1g of NaCl in 1 gallon of RO\DI water should test 264.17

2g of NaCl in 1 gallon of RO\DI water should test 528.34

Edited May 18, 2021 by Mmiller2001

[Tyler LaZerte]

@Mmiller2001 I will test it out when I go home. Thank you!