# API freshwater master kit - nitrite test...



## Rhinox (Sep 10, 2009)

I'm 3 weeks into my fishless cycle process. Ammonia is already dropping to 0 after 24 hours so I've been waiting for nitrite to do the same for about a week now.

I think I am getting close, but I have a question about reading the API nitrite test, for those who use the API kit.

OK, so when I test my regular tap water which I know has 0 nitrites in it, when I put the drops in it starts out blue, and remains blue after 5 minutes. The test says to allow 5 minutes to color up. When I first started reading nitrites in the water, when I put the drops in they immediately turned purple and stayed that way (I think). Since then, I've been dumping it as soon as I saw the purple because I assumed that meant I still had nitrites. Today, when I put the drops in, it again immediately turned purple, but I was being lazy so I just left it sitting out. Probably 10 minutes later, I glanced over and noticed that the vial looked blue. When I held it up next to the test card, it didn't quite match 0, but it wasn't even close to the first concentration (.25ppm).

So I'm just curious as to whats going on? how should the test vial look when nitrites are at 0? would the vial begin and stay blue, or should it start out purple and then turn to blue?


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## Morpheus (Nov 12, 2008)

I would say you still have nitrites. When I cycled my tank, I would test daily. As soon as I saw purple, I knew I had nitrites. But I also never let it sit for more than five minutes. After about two weeks of getting purple..purple..purple..one day it was just blue.

Perhaps one way to check would be to test for nitrates?


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## Rhinox (Sep 10, 2009)

Morpheus said:


> I would say you still have nitrites. When I cycled my tank, I would test daily. As soon as I saw purple, I knew I had nitrites. But I also never let it sit for more than five minutes. After about two weeks of getting purple..purple..purple..one day it was just blue.
> 
> Perhaps one way to check would be to test for nitrates?


I think you're right, I'd say I still have nitrites, I'll just keep checking until I see blue again as soon as the drops go in. I know with tap water it starts and stays blue, so I should expect the same when the tank has 0 nitrites. The only difference between the tank and tap water though would be the presence of nitrates if my tank were fully cycled, so I didn't know if it were something funny like the nitrates being the cause from the color change from purple to blue.

I'm not going to bother testing nitrates just yet. I remember hearing somewhere that the nitrate test will give a false reading if you have nitrites because I think the process for testing nitrates first changes the nitrate into nitrite or something like that, so whether or not I still had nitrites right now, I should get a nitrate reading.

Just another 6 days until I hit the 2 week mark since the ammonia dropped so it won't be long now anyways.

Thanks for the help


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## Toby_H (Apr 15, 2005)

While I do have an API test kit, and have had several int eh past... I'm not sure that I've ever done a Nitrite test and actually had nitrites in the water... So I can't give a simple experienced reply, sorry...

But my thoughts on the topic are... if the manufacturer suggests the accurate reading is to be taken 5 minutes after adding the drops, I'd trust the results that come 5 minutes after adding the drops...

I could see the drops turning the water blue if there is 0 nitrate... then staying blue...

but turning the water purple with any trace of nitrites, then fading... with the accurate reading being available at the 5 minute mark...

Like I said, I don't know for sure this is the case... but I would have to imagine there is a reason why the manufacturer recommends waiting 5 minutes...


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## DrgRcr (Jun 23, 2009)

Rhinox, I went through the same thing when I cycled my 1st tank. If the drops go in the tube and turn purple immediately, you are still high off the charts. When I experienced this, at 5 minutes the tube would appear to be a slight blue, misleading you to think it's 0. Then it would turn pale green, then almost clear a few minutes later. When the drops go in blue and stay that way at 5 minutes, you're done. When I cycled my second tank, I didn't even wait the 5 minutes if they went in purple.


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## K20Z3 (Jul 18, 2008)

I also had the exact same thing happen. Your nitrites are off the chart.

Like mine, they are so high that it is probably keeping the bacteria from growing. To get mine to cycle, it did about a 70% water change and within 2 days my tank was cycled.

You might want to give that a try?


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## Rhinox (Sep 10, 2009)

Thanks everyone for the confirmation - just what I though :thumb:

*Toby*: I don't know why the manufacturer recommends waiting but I assumed it would be like the ammonia test - starts out at a reading of 0 and then gradually darkens in color up to the correct value. So it through me off when it started off the charts and then lightened up to 0... :? I'm not really all too concerned what the value is, so I'll just wait until the drops start and stay blue.

*DrgRcr*: That is really weird I didn't know it would change through so many colors like that. Like you I had been dumping it immediately when it turned purple, but this time I just was being lazy and left it sitting there while i hopped on my computer and when I remembered to look back over, there was the blue vial. I bet this is what is happening when people think they have a cycled tank but they report the nitrites are like 0.05 or something.

*K20Z3*: Thanks for the water change suggestion. I have actually been considering it myself, but I thought I'd wait it out. Earlier I was thinking about starting a thread asking if anyone knew or could speculate the ideal concentration of nitrite for growing the nitrobacter bacteria, like how the nitrosomonas seem to do best between 2-5ppm ammonia. Theoretically, you could do a water change to reduce the nitrites to the ideal concentration and get the tank to cycle quicker. In the end, I decided I didn't have any reason to be in a hurry, so I figured I would just let it go. I still have another 5 days to go until I hit the 2 week mark since my ammonia dropped, so I'm not really expecting my nitrites to drop until then. If they haven't dropped by the end of the month, then maybe I'll have to try a water change.

The other thing I realized about a water change is that the bacteria start out free floating in the water, so a water change could actually hurt the cycling process if the nitrite concentration doesn't matter. Your post is actually the first I've heard about a too high nitrite level retarding bacteria growth... I cycled my tank to a low ammonia level (only 2ppm), so my nitrites should be lower than most who have been just fine without doing water changes to control nitrite, so I think my tank will cycle just fine within the next week. If not though, expect me to be right back here trying to figure out whats wrong 

anyways, I've noticed over the past few days that my water has started to become a little hazy (not bad, but definately not as clear as when I first filled the tank), which is a sign that I think I'm about ready to get a big bacteria bloom and then I'll be cycled.


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## K20Z3 (Jul 18, 2008)

I understand why you want to wait.

I just got tired of waiting. My cycle was one day shy of 8 weeks! I was willing to try anything at that point!


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## MalawiLover (Sep 12, 2006)

The reagant for the nitrite test beging breaking down after the 5 minute mark and with less reaction happening, the water fades back to blue than slowly out to clear if left long enough.


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## Rhinox (Sep 10, 2009)

So, I tested my nitrites again today. I followed the API test instruction to the letter. Drops went in and immediately turned purple. At exactly the 5 minute mark, I checked the vial and it was a shade of blue not quite matching 0, but not at all a purple color like all of the colors on the scale. It kinda has a greenish hue. At the 10 minute mark, the vial is still the same shade of blue.

I know there are still nitrites because the drops immediately turn purple when they go in. But, if I wouldn't have previously tested my tap water and known that the vial starts and stays blue when there are 0 nitrites, I'd be tempted to think that my nitrites had dropped to 0.

So basically, it seems like the test instructions are just wrong. Since the color at the 5min mark isn't an accurate reading, and the color gradually changes over the 5 minutes, it seems like it would be impossible to ever get an absolute reading. It seems like the test is only good for giving a yes or a no on whether nitrites are present.

Otherwise, maybe my drops are just semi-faulty?

By the way, at the 20 minute mark now and the vial is still the same shade of blue...


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## Toby_H (Apr 15, 2005)

If you really want to figure this out, I suggest using a different form of test and comparing results. Such as the dip strips.

While it is often stated that dip strips are not accurate, they will easily be able to tell the difference between very high nitrites (as suggested by the purple color first seen) and no nitrites (as suggested by the blue color at the 5 minute mark)...

I can definitely see how you would come to the conclusion you have... yet it's hard for me to believe that API's instructions are just plain wrong...

Therefore I do not think in this thread enough exploration has been made to make any determinations...

It is very interesting though...


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## K20Z3 (Jul 18, 2008)

Rhinox said:


> So, I tested my nitrites again today. I followed the API test instruction to the letter. Drops went in and immediately turned purple. At exactly the 5 minute mark, I checked the vial and it was a shade of blue not quite matching 0, but not at all a purple color like all of the colors on the scale. It kinda has a greenish hue. At the 10 minute mark, the vial is still the same shade of blue.
> 
> I know there are still nitrites because the drops immediately turn purple when they go in. But, if I wouldn't have previously tested my tap water and known that the vial starts and stays blue when there are 0 nitrites, I'd be tempted to think that my nitrites had dropped to 0.
> 
> ...


There is nothing wrong with them. Mine did the exact same thing! Your nitrites are just off the chart. Trust me :thumb:


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## Rhinox (Sep 10, 2009)

*K20Z3*: Yeah I know they're off the chart. This thread isn't really about me being worried about my nitrite levels more so than it is me figuring out why the API nitrite test seems to be misleading or incorrect.

*Toby*: I took your advice and got the tetra 5 in 1 test strips, and it did indeed turn a very bright pink color indicating the nitrites are off the chart.

When I finally dumped the previous vial about an hour in, it was still the same shade of blue.

So, this is as far as I'm probably going to take it. I will conclude that the API test is a good yes/no indicator of nitrite by watching what colors the drops are as soon as you add them, but if you follow the test directions and wait 5 minutes, I don't see how there can be an accurate absolute reading.

One thing does concern me a little... it seems the 5 in 1 test strip alerted me that over the course of the month I've been cycling my tank without doing water changes, my pH level has dropped. The color on the test strip didn't even change, which would mean the pH is around 6.4. I double checked with the API test kit and the tetra drip kit I have and the best I can conclude is that my tank pH has dropped to about neutral. I have seen a drop in KH as well, which should happen if the pH drops. My tap pH to the best I can tell is around 7.4. I started a thread a while back asking if I needed to buffer and the conclusion was that I didn't need to.

The best I can tell is that my tap pH is around 7.4. Can I rely on weekly water changes to keep my parameters in line once I have fish, or should I reconsider buffering?


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## kjhydock (Apr 28, 2009)

Rhinox said:


> One thing does concern me a little... it seems the 5 in 1 test strip alerted me that over the course of the month I've been cycling my tank without doing water changes, my pH level has dropped. The color on the test strip didn't even change, which would mean the pH is around 6.4. I double checked with the API test kit and the tetra drip kit I have and the best I can conclude is that my tank pH has dropped to about neutral. I have seen a drop in KH as well, which should happen if the pH drops. My tap pH to the best I can tell is around 7.4. I started a thread a while back asking if I needed to buffer and the conclusion was that I didn't need to.
> 
> The best I can tell is that my tap pH is around 7.4. Can I rely on weekly water changes to keep my parameters in line once I have fish, or should I reconsider buffering?


It's been a little while, so I apologize if my information is wrong, but I believe pH will the longer the water remains in the tank. I can't remember exactly what causes it, but I think it's the prolonged presence of nitrates that causes the pH to steadily drop over time. The information regarding that is somewhere in the forums and I apologize that I don't have the time to find it.

Regardless, if 7.4 pH is acceptable for what you plan on keeping, then you shouldn't worry too much about buffering as long as you do regular water changes once you are stocked.


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## K20Z3 (Jul 18, 2008)

Rhinox said:


> *K20Z3*: Yeah I know they're off the chart. This thread isn't really about me being worried about my nitrite levels more so than it is me figuring out why the API nitrite test seems to be misleading or incorrect.


It's because the regent is calibrated to measure a certain amount. If the test subject is WAY over that amount, the regent isn't going to be able to react how it was designed to act.

The majority of fish keepers that API sells the kits to don't "fishless" cycle their tanks, so they never see nitrites that high. If they did, all the fish would be dead and gone. It only "needs" to be able to measure a fairly low level of nitrites to please 99% of their customers.

I hope that makes sense???


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## Rhinox (Sep 10, 2009)

K20Z3 said:


> Rhinox said:
> 
> 
> > *K20Z3*: Yeah I know they're off the chart. This thread isn't really about me being worried about my nitrite levels more so than it is me figuring out why the API nitrite test seems to be misleading or incorrect.
> ...


That does make a lot of sense in some ways, but in other ways not.

For example, ammonia goes from yellow to green. The higher concentration of ammonia, the darker the green. Even if you go off the chart, the color maxes out at a very deep green color - it doesn't go back to yellow. Same with the nitrate test - goes from yellow to orange to red - higher the nitrates, the darker red the solution gets. I just expected a similar thing to occur with the nitrite test. If it goes from blue to darker purple as the nitrite concentrations increase, I would expect if the levels are off the chart, the color should just be a dark purple color - not a color that appears to be 0ppm.

So yeah, it makes a lot of sense that the test would be unrealiable at levels the kits weren't intended to test for, and anyone fish in the tank would have been long dead. But it makes no sense that a off the chart high level of nitrite would give a false 0 nitrite reading if the test instructions were followed correctly. :?

Anyways, I'm glad I bought the 5-in-1 test strips. Its much more convenient to dip the strip and see if the little pad turns pink than it is to get out a vial, rinse it out, rinse out a syringe, try to get 5mL, add drops, wait around, and get false readings  Since I don't need an absolute reading and just a yes no indicator of nitrites, in this application, the strips are far superior to the drops.


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## DrgRcr (Jun 23, 2009)

When I went through this, I did a water change to get them down to a readable level. This reassured me that I still had plenty of nitrite to remove at that point.


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## Dj823cichild (Mar 30, 2009)

Getting any better Rhinox?


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## K20Z3 (Jul 18, 2008)

It's a different chemical regent and the other two tests you mention are both two part regent tests, the nitrite is a single regent test.

I'm sure a chemical engineer could explain it better, I'm just an old electrical engineer. All those chemicals make my brain hurt thinking about them.

Maybe someone with a chemical background can chime in and explain it to us. You might also try posing this question to API? They have a feedback on the website and are really good about answering questions.

Brian


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## Rhinox (Sep 10, 2009)

Thats a good idea about contacting API... I might just do that to satisfy my own curiosity.

Dj823cichlid, things are about the same tonight. Tomorrow is really the first day I would expect the nitrites to drop to 0, so I'm not panicking or anything. If the nitrites don't drop by next weekend, I will try a water change to reduce the concentration and see if that helps. But, I have nitrates, so I know i have some of the bacteria I need... its only a matter of time I think. No rush necessary, I'm not in any hurry.

DrgRcr, the test strips that I bought prove that I still have nitrites. However, I may experiment with a water change if they don't drop to 0 next weekend due to the theory that too high of levels of nitrite may actually stunt bacteria growth. I truly don't think it will be necessary though.


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## Dj823cichild (Mar 30, 2009)

Remain patient. I remember when I was in your shoes it was very frustrating cause you want to add fish and you can't cause your cycle isn't complete. I feel your pain.


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