Fishless cycling in progress, big drop in nitrates overnight

[altidude]

I've been doing a fishless cycle on a new 10 gallon tank we're setting up at our office. I'm testing daily using the API freshwater kit.

The cycle was going great and on track per the "almost complete guide to fishless cycling" FAQ on this site.

Last night for some reason the nitrate level dropped from 80 PPM to 5 PPM. Same result on two tests.

Ammonia is dropping from 4 PPM to near 0 PPM over 24 hours as expected. Nitrite is reading at least 5 PPM, also as expected.

PH also dropped overnight from what was a steady 8.4 to 8.2.

I will be doing a 50% water change tomorrow.

Any idea on what would cause the nitrate level to drop so much over 24 hours?

 

[coralbandit]

Are you shaking the #2 bottle before adding drops? Not doing so will often give a false low reading..
Nitrates only go away two common ways that I know of.
Water changes ,or plants.
Do you have plants in the tank/
IMO they would not consume that much that quickly but?

 

[Mebbid]

I agree, even in a super heavily planted tank the nitrate will not drop that quickly.... unless someone snuck in and did a water change for you (wish they would do that for me) then it's very likely the test was performed incorrectly.

 

[altidude]

Thanks for the reply. Yes, I shake that number 2 bottle like a madman for at least forty seconds then the test tube for another one minute after adding the ten drops from the number 2 bottle.

I've been using the API kit for about a year on our tank at home and I've never seen this happen.

The 10 gallon tank is not planted by the way.

 

[altidude]

I agree, even in a super heavily planted tank the nitrate will not drop that quickly.... unless someone snuck in and did a water change for you (wish they would do that for me) then it's very likely the test was performed incorrectly.

Yeah, I thought I did the test incorrectly too. That's why I did the second test (carefully) and got the same result. I thought I may have added drops from the wrong bottle but that wasn't the case.

Water changes at this office aren't easy to do so it would be nice if I have a water change fairy but I don't think that's the case.

 

[altidude]

I just did a third test and got 5 PPM nitrates again.

If nitrates are over what the test can show (160 PPM per the chart) would the test show the 160 PPM color? The reddish brown?

Regardless, I'll do the 50% water change tomorrow since the PH is starting to drop and I'll also bring the kit from home and see what that one shows prior to the water change. Interesting stuff.

 

[coralbandit]

The test gets darker if the numbers are above..
No mistaking it..
Could this test kit be expired?
The dates should be on bottle.

 

[altidude]

The test gets darker if the numbers are above..
No mistaking it..
Could this test kit be expired?
The dates should be on bottle.

It's a new test kit. The dates are 07/2022

 

[altidude]

I brought the test kit from home and read nitrate at 5 PPM using that kit as well. I'm thinking the 80 PPM readings that I saw were not accurate.

The cycle seems to be on track. Ammonia drops from 4 PPM to near zero in less than 24 hours and nitrites read 5 PPM or higher (I think they're off the chart).

I did a 50% water change this morning based on the PH drop. I think it just needs more time for the nitrates to read higher.

Thanks for your input. I appreciate it!