HIGH Nitrate reading with API kit in Fish-only tank. Are there interferences?

[Richard Terrell]

I have a client that has been getting off-the-chart high nitrate readings in his fish-only tank for over a month. He's been doing ~30% water changes 2-3 times/week for the last month with no change in the reading. I did a 1:10 dilution and it was still reading off the chart. While I realize API is not super-accurate, it's usually good enough for this application. Might there be some weird interference giving a high reading? After all those changes, is it possible that his nitrates are still 1600+? His source water is reading <5 with API so while it's not zero, I'd have expected an improvement by now. Could StressCoat or Prime be giving these high readings (he's used both)? Has anyone had issues with IO having nitrates? I plan to test his salt on a return trip using some of my RO.
Thanks in advance!

 

[Dan_P]

I have a client that has been getting off-the-chart high nitrate readings in his fish-only tank for over a month. He's been doing ~30% water changes 2-3 times/week for the last month with no change in the reading. I did a 1:10 dilution and it was still reading off the chart. While I realize API is not super-accurate, it's usually good enough for this application. Might there be some weird interference giving a high reading? After all those changes, is it possible that his nitrates are still 1600+? His source water is reading <5 with API so while it's not zero, I'd have expected an improvement by now. Could StressCoat or Prime be giving these high readings (he's used both)? Has anyone had issues with IO having nitrates? I plan to test his salt on a return trip using some of my RO.
Thanks in advance!

Nitrite comes to mind as the likely interfering chemical species.

 

[Richard Terrell]

Nitrite comes to mind as the likely interfering chemical species.

Nitrite tests 0

 

[taricha]

Might there be some weird interference giving a high reading? After all those changes, is it possible that his nitrates are still 1600+?

1600? the color card goes up to 160. Typo? or are you saying a 1/10th dilution with distilled water reads ~160?
Other than nitrite interference, which you addressed already, I have no good ideas, only "bad test kit" and "user error" as give-up explanations.

 

[Dan_P]

Would the fish be sick at 1600 ppm?

 

[Richard Terrell]

1600? the color card goes up to 160. Typo? or are you saying a 1/10th dilution with distilled water reads ~160?
Other than nitrite interference, which you addressed already, I have no good ideas, only "bad test kit" and "user error" as give-up explanations.

1:10 dilution with RO reads 160+. Therefore tank is reading 1600+.Test kit appears accurate on other tanks. And while I'll never say I'm perfect I've been using these test kits for decades so I think I've got that covered. Both the API and Red Sea use the same reaction and have given similar numbers. I'm going to try to get a sample run with a cadmium reduction nitrate test to see if it agrees. I found out since that this area has chloramines in their water. So is possible every water change and topoff is adding ammonia which the tank is processing to nitrate.