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Weird Nitrates!

J

jazzsam

So I wanted to know if anyone has seen this before.

I tested earlier today to find my Nitrates around 100PPM. I started getting water ready to do a large water change and noticed I needed to top off about 5 gallons.

I tested the Nitrates again after the 5 gallon top off and they were around 40-50PPM........!

I used 2 different test kits to make sure I am doing this correct after hearing about certain test kits not working correctly.

Could 5 gallons of RO/DI water make this difference? I think that is crazy!

(I am still planning a large water change tomorrow)
 
Phyl

Phyl

Officer Emeritus
Officer Emeritus
What brand of test is it? I wonder if it is calibrated for a certain salinity and the salinity being off confused it into thinking the salinity was higher?

I would take a water sample, add more RODI and then run the test again to see if it reduced it beyond the ratio of fresh RO/DI to the sample as happened to your initial test.
 
D

DaveK

Perhaps you didn't do one of the tests quite correctly. Repeat the tests, and if possible use a different brand of test kit.
 
J

jazzsam

The tank is about 300 gallons total water volume.

I tested with 2 test kits both times so I find it hard to believe that I messed up with both and they still matched. One is a fresh/salt water test kit that uses liquid to mix with and the other is a Salifert test kit. Both said over 100 before the top off and then both said around 50 after it! That is why I am so confused!

The only other variable that I can think of is time of day but that really should not matter as far as I can see. I am going to test right before my water change and then after again just to see what happens.
 
H

hayabusa2003

Did you measure again an hour or so after adding the RO water? I would think it would take some time for the RO water with lower SG to thoroughly mix with the salt water in your tank, especially 300 gal. I know whenever I top off, i get different readings from if I were to wait a few hours and take measurements.
 
J

jazzsam

hayabusa2003 said:
Did you measure again an hour or so after adding the RO water? I would think it would take some time for the RO water with lower SG to thoroughly mix with the salt water in your tank, especially 300 gal. I know whenever I top off, i get different readings from if I were to wait a few hours and take measurements.
Click to expand...

I was thinking about that also. Maybe I could have gotten a sample of more clean water just by chance? I am going to do the water change today and I will test after that and then test again in a couple hours.
 
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