QuestionWeird cycle water parameters

Yannick

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I'm in the 4th week of my cycle and notice a pattern of weird parameters. I am wondering if these are normal or not...
From what I understand from the cycle, these values don't make much sense to be honest...

On the 29th of Feb I added 5ppm ammonia to the tank. Before I added that, both ammonia and nitrite where at 0. Nitrate was a 1ppm. The day before it was 100ppm nitrate and 0 ammonia and nitrite so I did a water change to get rid of the nitrate from the last ammonia I added.
From my understanding and references online 1ppm ammonia converts to 2.7ppm nitrite which converts to 3.6pppm nitrate.
This means that if my nitrite is 0 and all the ammonia has been converted, I would end up with 5*2.7=13.5ppm nitrite. This should convert to 18ppm nitrate.
Please correct me if I'm mistaken on this part... I just did these calculations to try to make sense but a lot of my confusion comes from this...

On the 1st of march, the reading showed 0.1 ammonia, 7ppm nitrite and 50! nitrate.
From my conversion above, I deduct that 4.9 ammonia has been converted to nitrite which should result in 13.23ppm nitrite. Because I only measured 7, it means that +/- 6.23ppm nitrite has been converted to nitrate. This should read as 8.3 nitrates so how is it possible that I read 50 nitrate?

The next day (2nd of march, yesterday): ammonia: 0, nitrite: 5, nitrate: 50
This also surprises me... Only 2ppm nitrite has been converted...

Today: ammonia: 0, nitrite: 0.4ppm, nitrate: 10
This completely baffles me... How can I see such a reduction in nitrite and a reduction in nitrate at the same time??? No water change has occurred since I added the ammonia.
I do have some plants in the tank but that shouldn't account for all that nitrate removal, right?

All the readings are between 20 and 24h in between.

It's not the first time that I see this occur during the cycle, it's actually the second time.
The pattern is this:
2) next day nitrite + nitrate spike where the nitrate spike is to high to account for the converted nitrite
3) next day almost no change
4) next day nitrite + nitrate drop

Can someone explain this behavior to me please so I understand what is happening in my tank?
One thing I am wondering that might explain the stalling of the nitrite on the second day is that I might overwhelm the bacteria that convert nitrite into nitrate and they are overfed after the first day and need to rest a bit for the second day?
This doesn't explain the nitrate spike...

If something in the water would cause nitrate to spill into the water, wouldn't I see an increase in nitrate each day and it shouldn't go down like I see?
Anyway, post is getting to long for all my questions...

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Yannick

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I really do have a weird cycle...
Just did a new reading, just to understand what is happening and see how it evolves...

So to recap... The reading around 2pm this afternoon: 0 ammonia, 0.4 nitrite, 10 nitrate
Did a reading now at 5:15pm so a good 3 hours later... nitrite dropped to 0.15 and nitrate dropped to between 3 and 5...

Chanyi

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Testing error and a real world vs math conversion fail.

How are you testing your Ammonia / Nitrite / Nitrate levels?

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Yannick

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I'm testing using a drop test. Initially I tested twice to double check I wasn't making an error.
I even tested with both drop and strip test and they both are in the same line.
If my drop test says 100ppm nitrate, the strip will also show a high concentration. If I see 10ppm nitrate, the strip also shows there is less.
The same with nitrite... So that validates that my testing is ok...

And what's the real world vs math conversion fail?
I can agree I'm misinterpreting the numbers for the conversion. I might even misreading some values on my test but I don't mistake a reading from 10ppm vs 100ppm for nitrate. And I won't misread 0.2ppm nitrite vs 5ppm.

But because I see this pattern happen twice during my cycle, I find it difficult to see how it's a test error. Especially since I redo the test if I see that the values don't make much sense...

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Yannick

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JBL Test: JBL Test CombI Set Plus NH4

I've read this on another forum:

Nitrate tests work by breaking nitrates down into nitrites first. Any amount of nitrites will appear as a larger amount of nitrates.
Not sure if this is true but this could actually explain everything... Because I had so many nitrite in the water, the nitrate test is off...
Only when there is little nitrite in the water, the nitrate test is accurate.

If this is true, I have my explanation and all is good... But I cannot seem to find confirmation online about this...

From wikipedia: Nitrate test - Wikipedia
A common nitrate test, known as the brown ring test[1] can be performed by adding iron(II) sulfate to a solution of a nitrate, then slowly adding concentrated sulfuric acid such that the acid forms a layer below the aqueous solution. A brown ring will form at the junction of the two layers, indicating the presence of the nitrate ion.[2] Note that the presence of nitrite ions will interfere with this test
I don't know what type of test my drip test is using but if it is using the ring test, I have found the cause...

Sorg67

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I tried to do similar math in a recent cycle and it did not work out as expected. I was getting a lot more nitrate than the conversion ratios suggested. I am not sure where those conversion ratios come from and I am not sure how accurate test for home aquarists are.

As ChanyI says, the combination between test accuracy and the vagaries of real world biologic functions makes the math difficult to tie out. Maybe possible in a lab with tighter controls and more accurate tests.

When you get your ammonia dosing to convert to nitrates with zero ammonia and zero nitrites, I would call it good.

5.0 ppm ammonia sounds like a lot. Are you planning to stock the tank very heavily?

Where in Belgium do you live. I lived is Schoten near Antwerp from 1970 to 1974.

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Yannick

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Yes 5ppm is a lot... I didn't know how much to add every time... When I started the cycle, I even added 10ppm... That took a long time to drop and ages for the nitrite to drop...

I just added some more ammonia to the tank as it all has been converted. Now it's 3ppm worth of ammonia. Hopefully by tomorrow this time it will have dissapeared and i'm good

The behavior I see is in line with the "nitrite mess with the nitrate test" concept as I always see a high nitrate spike when the nitrite go up and my nitrate go down as well when the nitrite start to dissapear.
The should add a warning on the test though... I messes with your brain during cycle. Once the tank has been cycled, there is no issue as you won't see such nitrite spikes that would cause the nitrate test to go wrong...

Sorg67 said:
Where in Belgium do you live. I lived is Schoten near Antwerp from 1970 to 1974.
I live in Gent. I wasn't born when you where here though

DuaneV

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I think you're reading into the numbers too much.

What happens when you're doing a fishless cycle with pure ammonia, you start dosing around 4ppm give or take. After a few weeks, once the Nitrosomas grow and start eating the ammonia at a good pace, the ammonia will start dropping and nitrites will start climbing. At this point the ammonia feeding is cut back by half, give or take, to 2ppm. Now your Nitrospira will start growing and eating the nitrites, producing nitrates. Once all ammonia and nitrites are reading 0 every day and you have nitrates only, your cycle is complete and you can add fish.

Dont worry about your conversions, where you think the nitrates should be, etc. If you put 2ppm of ammonia in the tank and the next morning you have 0 ammonia, 0 nitrites and nitrate levels you can read, you're cycled.

Sorg67

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Thanks for the information about the nitrite conflict with nitrate test. That is good to know.

I took my family to Belgium in 2002. We spent two weeks. Had a great time. Visited Gent while there.

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Yannick

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Thanks, I understand that process but that's also why I take it to far...
I'm a numbers guy. I like to understand what's going on and that's why I started to look into the actual conversion rates for ammonia to nitrate.
Taking daily water parameters and putting them in spreadsheet. It's part of the hobby...

If the numbers don't add up, I want to understand why and from what I learned now, I think I understand the numbers I've been seeing in my tank.