TDS and nitrates

[Jeffkhng]

Hi everyone
I am slightly confused here and hope that someone here can provide me some clarifications.
I understand Tds is the measure of dissolved solids in water. Like mg ions, sulphates carbonates etc
But is nitrates also part of this value? Eg TDS measures 150. API test kit nitrate shows 80 for example. Can I assume that 70 is the remaining for the rest of the stuff?

Thanks

[Jeffkhng]

Anyone?

[peewee1]

I think someone will eventually replay. The TDS in of itself is not an issue if the Ph, ammonia, nitrates and nitrites are acceptable. My tanks often run at over 900 TDS without issue or harshi8p on the fish. I would say to mind the ph, ammonia and the two ns and change water often.

[Second Hand Pat]

I did a little googling and

TDS - "Dissolved solids" refer to any minerals, salts, metals, cations or anions dissolved in water. Total dissolved solids (TDS) comprise inorganic salts (principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates) and some small amounts of organic matter that are dissolved in water."

TDS consists of major cations and anions (including nitrate).

In my experience TDS consists of kH and gH and this is what I care about. kH is your buffering for pH and gH is the mineral content of the water. Are you hoping the TDS increases when the nitrate increases? and perhaps indicates a water changes is needed?
Pat

[Jeffkhng]

I think someone will eventually replay. The TDS in of itself is not an issue if the Ph, ammonia, nitrates and nitrites are acceptable. My tanks often run at over 900 TDS without issue or harshi8p on the fish. I would say to mind the ph, ammonia and the two ns and change water often.

Thanks Peewee! Yup. I understand about keeping ph ammonia nitrites and nitrates properly. I was just thinking that day about it suddenly and I could not find some really obvious answer on google. Hence the question. ��

I did even notice spamming dechlorinator bumps up TDS quite a bit. Hence you are right. High TdS may not mean anything too bad.

[Jeffkhng]

I did a little googling and

TDS - "Dissolved solids" refer to any minerals, salts, metals, cations or anions dissolved in water. Total dissolved solids (TDS) comprise inorganic salts (principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates) and some small amounts of organic matter that are dissolved in water."

TDS consists of major cations and anions (including nitrate).

In my experience TDS consists of kH and gH and this is what I care about. kH is your buffering for pH and gH is the mineral content of the water. Are you hoping the TDS increases when the nitrate increases? and perhaps indicates a water changes is needed?
Pat
Hi pat!
Your right! I was hoping that the increase in TDS over a week assuming all else stays constant would be nitrate increasing. It’s so much easier to stick a tds pen then to run the api nitrate test!
I have tried tracking tds over a week and seem to observe that nitrate values raise in similar values. Hence wanted to hear what you people have to say about this!

[dspeers]

Hi everyone
I am slightly confused here and hope that someone here can provide me some clarifications.
I understand Tds is the measure of dissolved solids in water. Like mg ions, sulphates carbonates etc
But is nitrates also part of this value? Eg TDS measures 150. API test kit nitrate shows 80 for example. Can I assume that 70 is the remaining for the rest of the stuff?

Thanks

The simple answer is yes, nitrates constitute part of the TDS value, but with qualifications. TDS includes both ions which you listed as well as non-ionic dissolved atoms and molecules, such as glucose. The handheld TDS meters measure only electrical conductivity which is due to the number of ions dissolved in the solution (i.e. saline has a high EC/TDS vs fresh water). Even distilled water has a positive but false TDS value if exposed to air due to dissolved CO2 (a dissolved gas not solid). The meter then estimates the TDS from the EC.
Why are you asking? The safest way to know what your nitrate level is is to measure. But, you can use TDS to estimate nitrates once you have measured both several times in order to establish your correlation values given your water source. It would be worth rechecking periodically to validate your specific correlation values. Also depending on how long you go between water changes your measured EC will underestimate TDS due to increasing non-ionic organic molecules as well as ionic (an amino acid is much larger than a Cl ion but both have the same EC value)
FYI,Hanna will soon release a freshwater nitrate checker with digital readout for which I will be extremely grateful as I hate judging shades of color.

[peewee1]

Thanks Peewee! Yup. I understand about keeping ph ammonia nitrites and nitrates properly. I was just thinking that day about it suddenly and I could not find some really obvious answer on google. Hence the question. ��

I did even notice spamming dechlorinator bumps up TDS quite a bit. Hence you are right. High TdS may not mean anything too bad.

I do not know why it occurs but occasionally after working the TDS back down from 900 with daily water changes after a few weeks I can get it to the 200 range then a day or two later it shoots back to 900 again. Almost over night. The fish do not mind it and carry on eating normal, fighting, and spawning.

[Jeffkhng]

The simple answer is yes, nitrates constitute part of the TDS value, but with qualifications. TDS includes both ions which you listed as well as non-ionic dissolved atoms and molecules, such as glucose. The handheld TDS meters measure only electrical conductivity which is due to the number of ions dissolved in the solution (i.e. saline has a high EC/TDS vs fresh water). Even distilled water has a positive but false TDS value if exposed to air due to dissolved CO2 (a dissolved gas not solid). The meter then estimates the TDS from the EC.
Why are you asking? The safest way to know what your nitrate level is is to measure. But, you can use TDS to estimate nitrates once you have measured both several times in order to establish your correlation values given your water source. It would be worth rechecking periodically to validate your specific correlation values. Also depending on how long you go between water changes your measured EC will underestimate TDS due to increasing non-ionic organic molecules as well as ionic (an amino acid is much larger than a Cl ion but both have the same EC value)
FYI,Hanna will soon release a freshwater nitrate checker with digital readout for which I will be extremely grateful as I hate judging shades of color.

Hi Don!
Superb answer. I’ll have to read it a couple times more to really understand you. But I think I get you. Yes I still do my regular water changes. However it is much easier to use the TDS meter. But as you say. The relationship gets more inaccurate with longer time in between. I get it!
Thanks for much for writing the long paragraph!

[Jeffkhng]

I do not know why it occurs but occasionally after working the TDS back down from 900 with daily water changes after a few weeks I can get it to the 200 range then a day or two later it shoots back to 900 again. Almost over night. The fish do not mind it and carry on eating normal, fighting, and spawning.
I do also encounter this once in a while. However I do notice that it is typically always when I really muck around with the sand at the bottom kicking up a real mess. Maybe it’s related.

[gunnerschh2]

Just used nitrates test on my rift lake cichlids came out 0,tested discus tank also O NOW I WONDER IF up to date api test kit is right. I will get a hanna nitrate tester when it comes out.

[Jeffkhng]

Just used nitrates test on my rift lake cichlids came out 0,tested discus tank also O NOW I WONDER IF up to date api test kit is right. I will get a hanna nitrate tester when it comes out.
Wow! That’s super. Pray your test kit is working alright! I can only get Low nitrates

[Iminit]

Gunner did you shake the heck out of the second bottle? And the vial after mixing? Second bottle needs some heavy shaking!

[gunnerschh2]

Gunner did you shake the heck out of the second bottle? And the vial after mixing? Second bottle needs some heavy shaking!

Shook like crazy & on api 5.0 & on sea chem kit 5.o. First test was was 2 days after 80 persent water change today was a day before same water change. This was on 450g rift tank that is over stocked because of uncontrollable breeding. Both colors of 2 tests are so hard to read as others have said so come on hana meter. Tom Gunner was the name of my last great German German Shepherd. LOL

[dspeers]

Can't believe the nitrates are zero. The TDS jump is also a puzzle, although if the gH is high or there are other salts in the tank with relatively low solubility then messing around with the substrate will jump up the TDS. My understanding of the Hanna Nitrate checker was on the basis of a phone conversation I had with one of the company reps. But, I checked their website today and they recently released a low level (0-5) marine Nitrate checker, so I hope I did not misunderstand. Will be really upset as I love digital readouts and flat out hate trying to accurately judge color wheels. Sent them an e-mail and will update with their answer.
Just recalled a discussion with coralbandit in re using TDS as a water quality indicator. He has had great success and if you have ever looked at his ram breeding you will agree. Cannot recall the thread but you could pm him for feedback. By the way did not mean to suggest that TDS is not a good value to follow and is certainly easier to determine than nitrates, just that it is a little more nuanced than increased TDS = increased nitrates.

[Jeffkhng]

Can't believe the nitrates are zero. The TDS jump is also a puzzle, although if the gH is high or there are other salts in the tank with relatively low solubility then messing around with the substrate will jump up the TDS. My understanding of the Hanna Nitrate checker was on the basis of a phone conversation I had with one of the company reps. But, I checked their website today and they recently released a low level (0-5) marine Nitrate checker, so I hope I did not misunderstand. Will be really upset as I love digital readouts and flat out hate trying to accurately judge color wheels. Sent them an e-mail and will update with their answer.
Just recalled a discussion with coralbandit in re using TDS as a water quality indicator. He has had great success and if you have ever looked at his ram breeding you will agree. Cannot recall the thread but you could pm him for feedback. By the way did not mean to suggest that TDS is not a good value to follow and is certainly easier to determine than nitrates, just that it is a little more nuanced than increased TDS = increased nitrates.

The substrate idea was just a guess. I can’t verify that actually. You are right that for that to be happening maybe there’s undissolved salts sitting there. Seems unlikely though. ��

Thanks for all the replies. Much to learn!

[dspeers]

What else could it be? Remember the TDS is really an EC value which directly correlates to the # of free ions in solution. An almost immediate jump from 200 to 900 is hard to explain any other way.
Did make a misstatement earlier, indicated that an amino acid had the same effect per ion as an inorganic acid, similar value but not the same, pKa, temperature, and molecular size all play and each ion has a different EC vs concentration curve, and a different EC vs temp curve.

[Jeffkhng]

What else could it be? Remember the TDS is really an EC value which directly correlates to the # of free ions in solution. An almost immediate jump from 200 to 900 is hard to explain any other way.
Did make a misstatement earlier, indicated that an amino acid had the same effect per ion as an inorganic acid, similar value but not the same, pKa, temperature, and molecular size all play and each ion has a different EC vs concentration curve, and a different EC vs temp curve.
Hi Don. Don’t get me wrong. I don’t know these chemistry stuff too well myself. I just meant that substrates in the tank so how could it be undissolved if it’s already underwater. From a lay man point of view. You could very well Be right! Btw the tds example of 200 to 900 is actually someone else’s situation.
Cheers!

[dspeers]

Frankly, I am kinda guessing here but in a non-turbulent setting (as in the water below the top of substrate) you will get a gradient where there is a somewhat higher concentration of heavier substances, with subsequent precipitation of less soluble salts even underwater (that's why some older aquariums show lime stains below the water line). Stir it up and they return to solution. If that's not what's happening, I am at a complete loss as to what would kick up the TDS. Frankly, I am no chemist, just recalling what I learned as part of pre-med requirements. I get that your numbers are not the same as Peewee's, his are a puzzle. What are your #s pre and post substrate cleaning?

Anyone else have an idea what would cause such a big change in TDS over a short time frame?

[eros111]

A TDS of 900 surely cannot be right ???

[eros111]

A TDS of 900 surely cannot be right @Peewee ???

[peewee1]

A TDS of 900 surely cannot be right ???

I get readings of 950 several times. Beginning at around 250 for several weeks it shoots up to over 900 TDS in one day. As I continue to make daily water changes each day the TDS will drop by 50 or more. Such as 950 then mid 800s then 600s until eventually back to the high 100s to low 200s where it will remain for a time. Then suddenly back to over 900. The water is clear and the fish do not notice it. Like I said the continue to go about their business of eating, chasing around, and preparing for spawning.

[dspeers]

If I were getting these readings I would get a second TDS meter, fairly cheap. If both read the same I would be at a complete loss.

[peewee1]

If I were getting these readings I would get a second TDS meter, fairly cheap. If both read the same I would be at a complete loss.

I suppose there could be such a thing as a faulty meter. I will look for one to buy.

[dspeers]

You know this is so bizarre, I would start checking my source of water prior to adding to tank. Google Hanna Primo TDS tester.

[Jeffkhng]

Ignoring the rare times I get the results from stirring the substrate. I only get huge jumps if I dump salt or dechlorinator.

[peewee1]

Ignoring the rare times I get the results from stirring the substrate. I only get huge jumps if I dump salt or dechlorinator.

This jump to 900 did follow a treatment of Prazzipro and salt. That could be the contributing factors.

[dspeers]

I agree, i think the salt could be it. Sea water has about 50X electrical conductivity and therefore TDS of average tap water.

[dspeers]

You can skip getting a second TDS meter.

[Jeffkhng]

This jump to 900 did follow a treatment of Prazzipro and salt. That could be the contributing factors.
It’s definitely the salt! You can even hit the thousands! Try dumping salt in to bucket and measure before and after! I never knew my handheld pen could read into thousands!