Nitrates above 100ppm and won't go down

[Ago24]

Guys I have a big problem and I can't find an answer.
This is the situatio; The tank is a 33G Cube with a sump, it has been running for almost 3 years with only a pair of clownfish and a purple dottyback (pseudochromis Fridmani). I started with Ocean Direct Sand and dry purple rock from Aquaforest, it also have a lot of biomedia from and older reef tank. I stopped testing and doing WC for about a year because i lost interest and the fish seemed to be just fine, very active and eating well. The light is a Hydra prime 16HD but it was set really low because i didn't have any corals and minimal algea was growing in this period of time.
Now i wanted to get things back on track to be able to introduce some corals so i started testing a couple of weeks ago.

kH 7 pH8.1 Salinity 1026\35ppt PO4 0.07 Temperature 26.5 C; NO3 was more than 75 tested with Hanna HR test.

So i did the first WC of 15L (4G) with a new 4 stage RoDi system and tropic marine pro reef (always used that salt).
Everything was the same but obviusly PO4 lowered to 0.02 and i still couldn't read NO3 because it was above 75ppm

I did another WC 3 days later, same quantity but still no changes in NO3

So 2 days later i did my third WC but this time a took out 20L (5G)
Now PO4 is 0.00 but i still can't read NO3.

I tried to use a different test to see if it was a reagent issue but i got the same result: NO3 higher then 100ppm

Is it possible then it was so high that even by changing 50L in a week i can't have a reading below 100?
If anyone have any suggestions i'm glad to try.

Thinking it was a RoDI water issue i went to the LFS and buyed 40L of RoDI water from them Just to have it as buffer.

 

[Randy Holmes-Farley Verified Community Expert]

It is possible it is that high, yes. Try diluting the the tank with with new salt water to bring the value on scale so you can usefully track changes.

 

[Bruttall]

I found the hanna nitrate test, of all of them, terrible, hard to use, not very accurate. Seems I read if the reagents get old they do not read correctly. I went back to the API test.

I still use Hanna for phos, calc, dkh, and mag though.

Do you have a dead fish under some rock in your tank by chance? or some dead CuC? good biofilter would convert that ammonia to nitrate, just throwing stuff out there.

 

[andrewey]

Exactly what Randy said- if your result is above the reference range, you have to get the result within range before you can proceed.


As an example, if your nitrate was 160, after your three water changes, you would still have a nitrate a little above 100ppm.

 

[Ago24]

I found the hanna nitrate test, of all of them, terrible, hard to use, not very accurate. Seems I read if the reagents get old they do not read correctly. I went back to the API test.

I still use Hanna for phos, calc, dkh, and mag though.

Do you have a dead fish under some rock in your tank by chance? or some dead CuC? good biofilter would convert that ammonia to nitrate, just throwing stuff out there.

No the last thing to die was a couple of nassarius but they were removed a year ago

 

[Ago24]

It is possible it is that high, yes. Try diluting the the tank with with new salt water to bring the value on scale so you can usefully track changes.

Thx randy i'll try a big water change and see if i can bring them to scale

 

[Reefering1]

Thx randy i'll try a big water change and see if i can bring them to scale

I believe he was suggesting you dilute the sample, by say half, to get a result within range. (Then multiply by 2 for actual value, if diluted by half)

 

[Dan_P]

Guys I have a big problem and I can't find an answer.
This is the situatio; The tank is a 33G Cube with a sump, it has been running for almost 3 years with only a pair of clownfish and a purple dottyback (pseudochromis Fridmani). I started with Ocean Direct Sand and dry purple rock from Aquaforest, it also have a lot of biomedia from and older reef tank. I stopped testing and doing WC for about a year because i lost interest and the fish seemed to be just fine, very active and eating well. The light is a Hydra prime 16HD but it was set really low because i didn't have any corals and minimal algea was growing in this period of time.
Now i wanted to get things back on track to be able to introduce some corals so i started testing a couple of weeks ago.

kH 7 pH8.1 Salinity 1026\35ppt PO4 0.07 Temperature 26.5 C; NO3 was more than 75 tested with Hanna HR test.

So i did the first WC of 15L (4G) with a new 4 stage RoDi system and tropic marine pro reef (always used that salt).
Everything was the same but obviusly PO4 lowered to 0.02 and i still couldn't read NO3 because it was above 75ppm

I did another WC 3 days later, same quantity but still no changes in NO3

So 2 days later i did my third WC but this time a took out 20L (5G)
Now PO4 is 0.00 but i still can't read NO3.

I tried to use a different test to see if it was a reagent issue but i got the same result: NO3 higher then 100ppm

Is it possible then it was so high that even by changing 50L in a week i can't have a reading below 100?
If anyone have any suggestions i'm glad to try.

Thinking it was a RoDI water issue i went to the LFS and buyed 40L of RoDI water from them Just to have it as buffer.

Is nitrite present?

 

[Randy Holmes-Farley Verified Community Expert]

I believe he was suggesting you dilute the sample, by say half, to get a result within range. (Then multiply by 2 for actual value, if diluted by half)

Yes. :)

 

[Ago24]

I believe he was suggesting you dilute the sample, by say half, to get a result within range. (Then multiply by 2 for actual value, if diluted by half)

Oh i never tought of it, i'm trying it rn. Btw i tested my RoDi water to see if it had any traces of NH3 and its has some, 0.03 more or less, Can it be the problem? Since it is being transformed into NO3 by the bateria?

 

[Reefering1]

Oh i never tought of it, i'm trying it rn. Btw i tested my RoDi water to see if it had any traces of NH3 and its has some, 0.03 more or less, Can it be the problem? Since it is being transformed into NO3 by the bateria?

Dan's question is of utmost relevance...

Is nitrite present?

 

[Ago24]

Is nitrite present?

I'll test for it too, but why are we interested in nitrite?

 

[Ago24]

I tried doing a test with 50% diluition but still got a 75+ out of range, so i did a 25% diluition and got a reading of 13.2ppm wich I can't wrap my head around. I'll try to repeat it and see if I messed up the test.

 

[Reefering1]

I'll test for it too, but why are we interested in nitrite?

Nitrite being present will make false high nitrate test results..

 

[Dan_P]

I'll test for it too, but why are we interested in nitrite?

A small amount of nitrite can interfere with the nitrate test, making it appear that there is a high concentration of nitrate

 

[Ago24]

A small amount of nitrite can interfere with the nitrate test, making it appear that there is a high concentration of nitrate

Oh ok, i'll check thank you

 

[Ago24]

So... I tested 3 times at 25%. I got 13.2 the first, 24.3 the second and 37.6 the third one.
I'm really confused.
btw I tested for nitrit and got a 0 reading so on that aspect we should be good.
Any idea on how to proceed?
The 50% test was still out of scale but the three at 25% suggest that i should have had a reading at 50%.

 

[Dan_P]

So... I tested 3 times at 25%. I got 13.2 the first, 24.3 the second and 37.6 the third one.
I'm really confused.
btw I tested for nitrit and got a 0 reading so on that aspect we should be good.
Any idea on how to proceed?
The 50% test was still out of scale but the three at 25% suggest that i should have had a reading at 50%.

Something is going wrong.
What did you dilute the aquarium water with?
What nitrate test are you using? The variability of results is unusually high.

 

[Ago24]

Something is going wrong.
What did you dilute the aquarium water with?
What nitrate test are you using? The variability of results is unusually high.

I diluted the tank water with a batch of new saltwater i mixed previusly in preparation for a WC.
Tested with Hanna checker HR being carefull to use the exact same procedure in all tests.
Idk man, this is making me feel dumb lol

 

[Ago24]

Just to be more precise:
The procedure I used is
After every test i washed the cuvette and dryed it both inside and outside with clean paper.
Then i rinsed it multiple times with tank water and mesaured 2.5ml using the pipette, after this i rinsed the pipette with the new saltwater i mixes previusly and filled the cuvette till it reached 10ml.
Then proceeded to make the test being carefull to use all the reagent present in the bag every time