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Very High Nitrate Test Results??

Alex121

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24 Feb 2021
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Hi, I am hoping someone can help me get to the bottom of why I am getting such high Nitrate Readings. I have a 300 litre high tech tank and am adding 25ml TNC complete a day, This equates to 1.25PPM Nitrate daily. However, using an API test kit the Nitrate Readings are 80ppm+ only a couple of days after a 75% water change. The tank is moderately stocked so I cant understand where all these Nitrates are coming from. Can anyone help?
 

John q

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Well nitrate testing kits aren't always super accurate so that's one possibility. (I also use api test kit btw)

Another possibility is your tap water ~ if we assume your test kit is accurate and you did a 75% water change and still have high nitrates, then logic dictates that either you had megaton levels of nitrate to begin with, or your tap water contains a fair amount.
You can get your local water report by searching online, that will show you the tap water nitrate content.

This might also be worth a read. High Nitrates (>120ppm)
 

Zeus.

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Test Kits well worth a read, I and many others dont test our water expect by watching our plants and Darrels Duckweed index is a great testing method
If you have recently started the tank and used a ADA aquasoil high Nitrate NO3 readings will be normal for some time, plus if using tap water you are also adding NO3 as it is is most water supplies, my tap water very quite a bit with the seasons.
If the Nitrite (NO2) levels are high then that's a problem, but high NO3 isnt an issue, cant remember what the upper limit is for NO3 but 80ppm is below it IMO

I have a 300 litre high tech tank and am adding 25ml TNC complete a day, This equates to 1.25PPM Nitrate daily

I take it you have used rotala butterfly

1617395243649.png


Which gives the N ppm not the NO3
1617395386631.png


So your adding about 40ppm NO3 a week with the TNC.

With a 300l tank would be well work getting a APFUK starter kit its in stock so dont wait too long
 

Alex121

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Hi, thanks for the responses. I checked my tap water and it is only around 4ppm. You are correct @Zeus I was using Rotala butterfly and had not realised that N was Nitrogen not NO3 that is a big difference! I suspect that it may have been building up as I was assuming I was putting in 1.25ppm. I am definitely considering the APFUK kit I like the idea of being able to control the ratios of ferts not to mention the savings!

Also just out of interest where its says 1.5% N on the TNC complete label what does that mean exactly? Does it mean w/v%? or put another way how many grams of Nitrogen does 1 Litre of TNC complete actually contain? I know the calculators do it for you but I am just interested in how to calculate the exact ppm directly.
 

dw1305

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Hi all,
1.5% N on the TNC complete label what does that mean exactly? Does it mean w/v%? or put another way how many grams of Nitrogen does 1 Litre of TNC complete actually contain?
It contains 15g of Nitrogen (N). That is 1.5g in 100 mL. multiply both sides by 10 and you get 15g in 1000 mL (one litre).

The 1.5% w/v% means there is 15g in the 1000 mL of "TNC complete". Because fresh water has a density of 1 (1 mL weighs 1g), and the TNC contains some salts the the litre will weigh slightly more than 1 kg, but it will only be a <"minor increase in density">, and we can work with "1g = 1 mL".

@Zeus.'s spreadsheet takes all the fun out of it, but you can work out the percentages of ions for any compound from the RAM of the elements and RMM of the compound. The workings for <"potassium nitrate (KNO3) are here>".

cheers Darrel
 

Alex121

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Thanks again @Zeus and @dw1305 this is really helpful. I am clear now on what the w/v% means. @dw1305 would you mind explaining how the slight error is introduced by assuming "1g=1ml" I understand the density of the TNC complete is not exactly 1 however if it was being added to water how would the error occur? for example lets suppose I add 10ml of TNC complete to 100 litres of water. 10ml contains 0.15g Nitrgoen = 150mg. So 150/100 = 1.5mg/L = 1.5ppm. I suppose technically you now have 100litres + 10ml so it would be 150/100.01 I assume this is considered negligible and not included in the fertiliser calculations?
 

dw1305

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Hi all,
So 150/100 = 1.5mg/L = 1.5ppm. I suppose technically you now have 100litres + 10ml so it would be 150/100.01..........I assume this is considered negligible and not included in the fertiliser calculations?
Yes <"I just ignore it">, and use weight and volume interchangeably for dilute solutions. Cold "water" ("dilute solution of salts with H2O as a solvent") is denser, so it is best to have everything at room temperature.

Even a salty solution (like <"sea water">) isn't much denser than freshwater.
...... The range of density in the oceans is from about 1.020 to 1.070 g/mL ...........

cheers Darrel
 

Alex121

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Thanks again really helpful, I am slowly getting my head round it all. I was wondering is there a way to use the fertiliser calculator to directly convert a 25ml does of TNC complete into NO3,PO4......ppm?
 

Zeus.

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Thanks again really helpful, I am slowly getting my head round it all. I was wondering is there a way to use the fertiliser calculator to directly convert a 25ml does of TNC complete into NO3,PO4......ppm?
Yes, just input tank size and your dosing regime
1617620196366.png


Then clone what ever is on the dropdown list, it will report if you go over salts solubilities by making it too concentrated.
The calculator works from the weekly ppm dose, I would class a 'true' clone as one being the same concentration as the product (so you dose the same amounts for product and clone and you get the same yields), a 'pseudo' clone isn't the same concentration, however both yield the same weekly ppms for the Macros and Fe, If you wont to match all the trace element concentrations then its time to roll up your selves and use the DIYTraceCaculator
 

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