TDS - Tracking Traces and Nutrients - Part 1 - The Planted Tank Forum
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 02-11-2006, 06:37 PM Thread Starter
Planted Tank Guru
 
unirdna's Avatar
 
PTrader: (3/100%)
Join Date: Jan 2004
Location: Madison, WI
Posts: 2,291
TDS - Tracking Traces and Nutrients - Part 1

Abstract:

Sparked by a conversation with Wasserpest , I've decided to perform an experiment to what kind of relationship nutrients and traces have on TDS (total dissolved solids). Bear in mind that ANY/ALL dissolved solids affect TDS. Yet, we only can inexpensively test our water for 5 these dissolved substances (KH, GH, Iron, NO3, PO4). My goal is to see how much impact the stuff we add to our tanks has on TDS in order to be able to roughly gauge how much "other stuff" is accounting for TDS. In other words, if we know that tank-water TDS is 600, and we can account for 400 of this TDS using tests for our 5 major compents, then we'll know that 200 of that TDS is made from things we don't test for. And, consequently, this can give us better insight as to whether we are overdosing the "untestables" (like trace minerals and potassium) in our tanks.

I yield that this is NOT an exact science. But, it is a means to gain some insight into the "untestable" aspects of planted aquaria.

Part 1 of this experiment will deal ONLY with individual nutrients and how they affect TDS. In the coming weeks, I will be adding a 2nd part to this experiment involving the long-term testing of TDS on my planted tank, and the impact plant uptake of nutrients has on TDS. Part 1 will set the foundation for part 2.

Equipment used:
Oakton meter, capable of measuring 0-1990 TDS.
500 mL bottle
1 mL syringe
RO water



Products tested:
Seachem Flourish
Seachem Iron
Kent Proplant (Iron and K)
Potassium Nitrate (mixed from dry ferts)
Mono Potassium Phosphate (mixed from dry ferts)



I started the experiment by simply pouring some Seachem Flourish into the cap of the container and taking a reading. My TDS tester read "error" because the TDS went over 2000.

So, I realized I'd have to do some dilutions. I added 1 mL of product solution to 500 mL RO water. The RO was tested each time prior to adding any products to ensure that TDS read 0.



After adding 1 mL solution of Flourish, the tester read 50 TDS. Therefore, Seachem Flourish has a TDS of 50 x 500mL = 25000 TDS.

I tested the other 2 commercial products

Seachem Iron read 110 TDS for 1/500th concentration = 55000 TDS

Kent Freshwater Proplant read 190 TDS for 1/500th concentration = 95000 TDS

Next, I tested my two nutrient mixes KH2PO4 (mono potassium phosphate) and KNO3 (potassium nitrate). The KH2PO4 was mixed to a concentration that would increase PO4 in my 46g tank 0.2ppm for each mL added. The KNO3 was mixed to a concentration that would increase NO3 in my 46g tank 1.0ppm for each mL added.



KH2PO4 read 70 TDS for 1/500th concentration = 35000 TDS

KNO3 read 420 TDS for 1/500th concentration = 210000 TDS

It may seem to some that because both chemicals contain potassium (K) which we can not test for, this portion of the experiment is riddled with error. But, in truth, it is not, since a TDS meter measures the K as well. So, while it is true that we can not measure the potassium individually, we can account for the total TDS that nutrients add as a whole to our aquaria. In other words, we can account for the things WE add to the aquaia. This applies to all things we add to our aquaria. A TDS meter measures it all.

Is this a vague way of assessing nutrients? ABSOLUTELY. But it does give us some means to gauge concentrations of traces, potassium, and other untestables.

For reference, my tap water has a TDS of 400 with the following parameters.
KH 20
GH 20
NO3 0ppm
PO4 0ppm
Iron 0ppm

The final part of part-1 of this experiment was to test if the sum of the 5 products' TDS added in one solution equalled that of the sum of the individual TDS readings.

Total of individual readings.
Flourish = 50 TDS
Flourish Iron = 110 TDS
Kent Proplant = 190 TDS
KH2PO4 = 70 TDS
KNO3 = 420 TDS
-------------------
Total = 840

One mL of each added to one 500mL solution = 790 TDS, giving us an error of about 6%. Close enough to surmise that this error most likely resulted from slight measuring error, and not because of a more complex relationship.

In part 2 of this experiment, I will practically apply these findings to the health and maintenance of the aquarium by monitoring how TDS increases and decreases with nutrient addition and uptake. Specifically, how to subtract TDS for testabe nutrient uptake in order to better understand the amount of "untestables" that have/have not been absorbed by the plants; giving us some insight to trace absorbtion.

Ted


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Set up April 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Terminated March 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
unirdna is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 02-11-2006, 06:55 PM
Are these real?
 
Wasserpest's Avatar
 
PTrader: (195/100%)
Join Date: Jun 2003
Location: Monterey, CA
Posts: 15,634
Interesting start... I liked your CO2 solubility experiment a lot too.

Any way you could include K2SO4 in your measurements?

I have been reading some more about the EC/ppm relationship. One is the conductivity of a solution, one is the dissolved content in it. They are closely related, but EC is influenced by the temperature of the water and other things.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Wasserpest is offline  
post #3 of 8 (permalink) Old 02-11-2006, 07:06 PM
Algae Grower
 
defdac's Avatar
 
PTrader: (0/0%)
Join Date: Dec 2003
Location: Linkoping, Sweden
Posts: 125
A fellow swedish aquarist have already done this experiment and it doesn't work because plants emit counter ions when uptake takes place (K+, H+) so you will not be able to measure any significant dip in the TDS.

The large transparent jug is tap, the green cup is after wc+PMDD and the red cup is after a couple of days. You can cleary see the difference in conductivity.
http://www.bluesboy.se/movies/tds.wmv
Not good.

At 19:15 a full dose of PMDD is dosed and you can clearly see how the conductivity raises significantly:
http://www.bluesboy.se/viewimage.php?id=411
Seems good.

But when it is hooked up to a computer-log the conductivity does not change to any significant extent so you can use it to see when to dose. Three days almost no change can be measured (the black line in the middle):
http://www.bluesboy.se/viewimage.php?id=412


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
defdac is offline  
 
post #4 of 8 (permalink) Old 02-11-2006, 07:07 PM Thread Starter
Planted Tank Guru
 
unirdna's Avatar
 
PTrader: (3/100%)
Join Date: Jan 2004
Location: Madison, WI
Posts: 2,291
Quote:
Originally Posted by Wasserpest
Any way you could include K2SO4 in your measurements?
Certainly, by taking a before and after [dosing] TDS reading of your tank, you could learn how much of the total TDS accounts for K2SO4. To get an even more accurate reading, dissolve the K2SO4 in water prior to adding to the tank and take a TDS measurement. This would just take a bit of math.

The problem you'll run into later is knowing how much of the "untestables" is the result of K2SO4. When it goes in the tank, it can be tested individually. This is the only time you'll ever be able to know exactly how much of the TDS is from the K2SO4 (or any added "untestable" for that matter). Later on, all you'll be able to know is the total TDS for all "untestables". Still, this will give us insight as to how much of the total is NOT N,P,GH,KH, or Fe.

It's a "ballpark science", if you will.

Ted


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Set up April 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Terminated March 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
unirdna is offline  
post #5 of 8 (permalink) Old 02-11-2006, 07:09 PM
Algae Grower
 
defdac's Avatar
 
PTrader: (0/0%)
Join Date: Dec 2003
Location: Linkoping, Sweden
Posts: 125
(This idea work though in hydrophincs because the nutrient solutions measured are much more concentrated)


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
defdac is offline  
post #6 of 8 (permalink) Old 02-11-2006, 07:10 PM Thread Starter
Planted Tank Guru
 
unirdna's Avatar
 
PTrader: (3/100%)
Join Date: Jan 2004
Location: Madison, WI
Posts: 2,291
Quote:
Originally Posted by defdac
A fellow swedish aquarist have already done this experiment and it doesn't work because plants emit counter ions when uptake takes place (K+, H+) so you will not be able to measure any significant dip in the TDS.
Very interesting, defdac. And, if true, this could potentially complicate our hopes of gaining useful insight re: unused traces and potassium [using a TDS meter]. I intend to analyze your links, possibly with the help of my friends in the chemistry department. I'll comment once I've digested the material. The first question that comes to mind: "is the ion exchange a 1:1 ratio with respect to TDS?".

Thanks for your input.

Ted


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Set up April 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Terminated March 2007 -
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
unirdna is offline  
post #7 of 8 (permalink) Old 02-11-2006, 07:15 PM
Algae Grower
 
defdac's Avatar
 
PTrader: (0/0%)
Join Date: Dec 2003
Location: Linkoping, Sweden
Posts: 125
(sorry for all the editing of my first post, i got the description of the cup content all wrong)
Quote:
Originally Posted by unirdna
The first question that comes to mind: "is the ion exchange a 1:1 ratio with respect to TDS?".
It seems so, which is unfortunate


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
defdac is offline  
post #8 of 8 (permalink) Old 02-11-2006, 07:22 PM
Planted Tank Guru
 
plantbrain's Avatar
 
PTrader: (267/100%)
Join Date: Dec 2003
Location: The swamp
Posts: 13,609
I had the same issue, the TDS did not vary much.
Hopeful thinking, but a no go.

If you have high evaporation rates like in hydroponics, it does work.
But we don't.


Regards,
Tom Barr



plantbrain is offline  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome