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Tds Vs Nitrates

Discussion in 'Cherry Shrimp' started by tjander, Apr 15, 2019.

  1. tjanderWell Known MemberMember

    I realize this post might be better put other places, but my reason for putting it here is we really watch DTS on the shrimp, so I am expecting a more informed answer here.

    So I tried an experiment yesterday, I changed out 50% of my water with tap water. Prior to doing this I measured my nitrates they were in the 40’s area. I also checked my TDS and it was 500. Both higher then I like.
    after about 6 hours doing my water change, my nitrates were down in the 20 or 30 range and my TDS was 260. Ok I am thinking success right?
    We this morning before leaving for my flight, I checked the TDS again and to my surprise it was up to 310. I did not have time to do nitrates but if I was a betting man I would bet they are also up.

    My question is this. Is there any correlation to TDS and Nitrates?

  2. FishRFriendzWell Known MemberMember

    Yes, but possibly not 1 to 1. TDS meters use electrical conductivity to estimate TDS. Some compounds have more or less conductivity.

    Side note: Chlorine is not electrically conductive so a TDS meter cannot detect it.

    You must be feeding a lot to be having your TDS jump that much or using salt. Salt will make a TDS meter jump way up.

    Last edited: Apr 15, 2019
  3. richie.pWell Known MemberMember

    I'm not a chemist but my understanding of them is that they are separate to our water, the readings you got there were before and after the water change and the difference you are seeing on the second readings are a dilution state then this mornings reading is after a full mix with new and old water
    Did you check your source water tds & nitrates before the change, it still doesn't alter the fact I dont think they are correlated but there may be a chemist out there that will put us right

    I've just done a test first with RO water Test1 TDS=1 Nitrait came out =0 test Test2 I added minerals and brought the TDS=433 Nitraite 0 on that test theres no correlation at all

    Attached Files:

    Last edited by a moderator: Apr 16, 2019
  4. SkavatarWell Known MemberMember

    good read  
    "This includes your important things such as calcium, magnesium and carbonate that you can measure using your kH, gH, pH kits. However, it also includes all the other dissolved minerals, salts and more. Basically anything that is too small to be filtered out."

    nitrates is only 1 of the many minerals, salts, metals, etc that that falls under the category of "TDS"

  5. FishRFriendzWell Known MemberMember

    I bet he added fertilizer after the water change.
  6. richie.pWell Known MemberMember

    Never had to use it but do fertilizers have much affect on your water
  7. toosieFishlore VIPMember

    New and old water don't mix immediately in the tank. There is some immediate mixing, yes but not fully. Taking any reading immediately after a water change is likely going to be different than taking one after the waters mix completely. That includes nitrate testing and pH testing (if new water is at a different pH).
    If you had used RO water and added nitrates it would show up on the TDS. But you added minerals. You won't get a positive nitrate test adding minerals. Just like you won't increase your minerals by adding nitrate.

    This in part is why I don't solely use TDS, and I will still use GH and KH. With TDS, it could all be something like nitrates being detected. When I want to know how much calcium and magnesium, and carbonates, I use GH and KH. Plus if I know how much nitrates there are, I have a better idea how much other stuff is in the water besides those things by using TDS meters. Other things might includes iron, copper, zinc, phosphates, potassium, sodium, among others.
  8. FishRFriendzWell Known MemberMember

    It's pretty significant, enough that I don't bother using a TDS meter on the one tank I fertilize with an auto doser. A TDS reading on that tank is pretty much meaningless since there's no knowing how much is any given compound. The only way to test that tank would be to do individual tests.
  9. toosieFishlore VIPMember

    I actually find it amazing how many people rely on TDS meters alone, even in a planted tank.
  10. tjanderWell Known MemberMember

    So this really has gotten out of control. Thanks all for your input.
    Now let me say this I tested 6 hours after adding. Not right away, second it’s a 10 gallon tank, third, nothing else was added to the tank after the water change out side of Prime, fourthly, my tap water reads almost 0 nitrates and a TDS if 60.

    Now with all that said, I think somehow the conductivity of the water which is what TDS measures is tied to the nitrate levels. A chemical that is part of the nitrate reading must also conduct electricity hence raising the TDS reading. Or, could left over ferts that are in the tank be more slowly mixing with the water and causing the Conductivity of the water to raise.

    Now that I typed this out I am thinking number two is the likely cause. Anyway I will know in 4 days when I get back home and check the TDS and Nitrate levels.

    Also, I think it’s safe to say that TDS alone will not tell you everything you need to know about your water. I was hoping it would but I think I proved my own point.

    Thanks for the input all.
  11. richie.pWell Known MemberMember

    Please dont think it's got out of hand in fact quite the opposite with the input we've had, I think it a very constructive and informative thread
    Last edited by a moderator: Apr 16, 2019
  12. tjanderWell Known MemberMember

    Ok out of hand is maybe not the best choice of words. My apologies. There are all good points and as I have always said on here, you need to read everything and then decide what advise makes sense to your particular issue.
    Thanks again
  13. richie.pWell Known MemberMember

    With my shrimp tanks I use a tds meter every day as a guide to my gh, I know if my tds rises my gh dose as well and to get my gh to 5 with RO water I have a constant tds reading of 96 but these readings fluctuate between tanks none of them are the same , so in your opinion do tds and Nitraits have a bearing on each other
  14. toosieFishlore VIPMember

    Yes, they definitely do. But in a tank where all parameters stay pretty constant, if something is being added, a quick test with TDS before and after may be all that is needed. But if a variety of things are going on, all a TDS test can do is tell you how many total dissolved solids there are, but not what those solids are or in what ratio. It can't tell you if something in particular is lacking or if there is an over abundance of. If TDS is higher than normal, it might just mean you need to do a water change, but if you just added a fertilizer, you would want the TDS to be higher.

    As you used the TDS to add minerals to RO, that is a good use for TDS, because it allows you to add minerals to that same level again another time. Once it is in the tank though, some minerals will get used up, and some nitrates will get added in, so then the readings could look similar and yet in actuality be quite different.
  15. richie.pWell Known MemberMember

    I understand where your coming from as it's a constant battle of testing to keep my shrimp tanks the way I want, and the tds with my shrimp tanks is invaluable and even though I use a buffer substrait and RO water things never go high, I did make a big mistake once leaving my tds go to 250 in a crystal tank and my gh rose to 11 no critical by any means bt they stopped breeding now to keep them breeding its tds96 gh5 so for me the critical one is gh to low they have moult issues to high stop breeding,
  16. tjanderWell Known MemberMember

    So, here is a thought. If your TDS is measuring conductivity why should it change and why should it go up? If anything it should go down as plants and animals use up the compounds that allow for water to conduct electricity the water should be less conductive. Lower TDS.

    Now adding ferts would increase the conductivity and raise your TDS. So is this the answer? Is the ferts we put in the tank a bigger increase on TDS?

    This is all based on my electrical engineering knowledge of how electricity works. Not on any chemistry knowledge which I have virtually none.
  17. richie.pWell Known MemberMember

    I believe this is why RO water is non conductive as theres no tds which is needed this is why I dont get a problem, that's about as far as my knowledge goes
  18. toosieFishlore VIPMember

    This is actually correct, but evaporation has an effect as well. But as plants and animals use the minerals and carbonates, waste products they produce are added, so then this waste can show an increase in TDS, along with the effects of evaporation.
  19. tjanderWell Known MemberMember

    Well, yes and very good point, and I know you can’t take one factor out and simply ignore the others but for the sake of discussion.
    Evaporation will not deplete the elements in the water. So assuming the same volume of water is maintained ( you add neutral water to replenish the evaporation ) the TDS should stay constant. No?
    In regards to fish waste this proves a connection between increased TDS and Nitrates. No?

    Ok all of this said. Could the point be that we are relying on a very broad set of parameters to determine whether or not we have a healthy environment. I mean look at The color chart for nitrates the difference between 40 and 80 to my eye is undetectable, yet the reading is a double.
  20. toosieFishlore VIPMember

    Well yes, if evaporation is replaced with pure water, then minerals and carbonates would be less affected and so TDS would be less affected, but the plants and animals will still use minerals and carbonates, and decrease TDS that way. BUT plants die and decompose, animals eat food, and because of this both plants and animals make waste which then can increase TDS. And yep, I have been saying that nitrates are represented in TDS along with many other things. Bacteria also use carbonates, so that is another user that can help deplete them. The natural acids that develop in a tank that use up carbonates and bicarbonates play a part in changing the balance of TDS too. Everything in an aquarium is in a constant state of change, so the components that make up TDS are always shifting.

    A lot of people I come across like to use TDS as a way of determining how hard water is. But I maintain that it isn't a great way to determine this, because a heavily stocked tank can have a lot of nitrates in a fairly short amount of time, but having fish doesn't harden water, and neither do the nitrates. OR The tank owner might be using a water softener and have very soft water because of it, but have a very high TDS because of the amount of sodium chloride or potassium chloride present in the water from the ion exchange that happened in order to remove the calcium and magnesium from the water. Too many factors play into TDS to use TDS as the sole determining factor on water hardness, or water health for that matter. But it is a good tool, a useful tool, because it can tell you that things are going out of balance or straying away from what you would expect when compared to your source water. And if used before and after manipulating something in the tank, it can help you see the results.

    One of my main uses for my TDS meter is to determine when my RO membrane needs to be changed, because TDS will rise. In this case I really don't care what makes up TDS, past a certain level and that membrane is out of there!

    Using TDS is using something that does represent a very broad range of components. When we test an individual parameter, such as nitrate, we can start to develop a better picture of those components. In my opinion, using the upper ranges of the color charts are difficult for most people, but that doesn't negate knowing that by the time you are in the upper level of that color chart, that you have a whole lotta something there, and in your example, a whole lotta nitrates. If the lower end of the color chart is easier to read, when a level like nitrate is high, diluting the sample with pure water (or in this case just water with 0 nitrates) and doing a 50/50 mix, will cut the end result in half, possibly making for an easier match. But you have to remember to double the result.

    So having said that, yes we as fish keepers do use a small sampling of parameters to try to determine if we have a healthy environment. And sometimes they aren't enough.

    Edit: I edited to indicate "sodium chloride" and "potassium chloride" instead of just saying sodium and potassium. :)
    Last edited: Apr 16, 2019