Hello all,
I have a bit of a warning for all those fishless cycling and using API nitrite test kit. As i now know now I am in the middle of a cycle, but for the last four days I thought I was fully cycled as my API test was giving me a nitrite reading of 0 after initially being purple but fading to blue - the zero reading after the recommended 5 min waiting time. This is INACCURATE. In fact an initial purple (drops turn immediately to purple at bottom of test tube) and then fades to blue means that nitrite is off the scale and that the test is confused.

Im not sure if this is common knowledge but a fair bit of digging on other forums reveals other people have been having the same issues.

Just thought you all should know and be aware... Mods might want to post it somewhere more appropriate. Wouldn't want new fish keepers falling into the trap and getting fish early because they think their tank is cycled when it's at the peak of its nitrite spike

That's a worry ...

I think the Water life nitrite test kit can be helpful for cycling as it reads up to 15 ppm whereas the API one only reads to 5 ppm. You can ring them up and they will post it out very quickly.

Alternatively (thanks DaveGodfrey for pointing out the should-have-been-obvious-but -wasn't) you can use double the amount of water with the same amount of reagent and if you get a reading of 4 you know really it's 8 - etc.

Will move to general information and sticky, tx

Hi lydslikestea

I did think it a little odd when you indicated the tank had cycled by day 18, hence my previous post. A cycle is generally just under 4 weeks, sometimes a little longer as its a fixed biological process.

I've undertaken numerous cycles and haven't had this problem with my kit but thank you for flagging the issue. Something we can always newbies to check if they experience the same

Hi Violet, I was surprised by the length of time too. But was convinced that it was done as four days on the trot I had a zero reading.

It was only after I'd done several water changes to lower the nitrate levels that the nitrite reading showed purple. Then I got worried and started looking into it.

So I'm now taking my time and fiddling with landscaping (I'm gradually switching my substrate now that I've settled on having cichlids - bye bye gravel, hello sand and rocks) and I've added in food pellets for ammonia source this morning as I've heard that makes a more robust colony. I expect I'll be done cycling in a week or so... then I'm going to give it another week to make sure!! Fish are for life right

Happy to make people aware. I was pretty miffed with API but then if their tests are for maintenance and not cycling given their scale then they should point this out of their instructions/packaging

Pretty sure this explains my recent results. Last week my nitrite had dropped to zero, then it seemed to go back up to 5ppm, now it is going back down again. Perhaps the results last week were just false. Could have been bad.

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To be fair to API, none of the kits on the market are meant for cycling and none of them will mention it so there's nothing unusual about that. The levels of ammonia and nitrite reached in a fishless cycle using liquid ammonia are massively more than would ever occur in a tank stocked with fish, even cycling fish in. As yet, the industry hasn't taken fishless cycling on board so there is very little in the way of commercial products to assist.

Waterlife ammonia and nitrite test kits do what they need to do if you are cycling with Biomature as that is also their product, but I think that is the only example of this.

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that's a good point. still don't really get why fishless cycling (or even the nitrogen cycle) is still so unspoken about in fish shops / product manufacturers.

Hi Everyone

When I saw this thread I mentioned it to the Head of Scientific Affairs at API. He wrote me a response, which I thought I'd post here for people to read.

Ranges for chemical measurements have limits. The lower limit is important because it determines whether a measurement is different from zero. The maximum Test Kit Detection Limit is important because this is the upper limit that any test kit can provide an answer for 99% level of confidence. All API Test Kits show the detection limits clearly on the packaging, instructions and colour charts.

API Test Kits are designed for use under normal conditions found within an aquatic environment (aquariums and ponds). The tests allow for, and are designed for, interferences and limited detection limits. When test results appear inaccurate, develop an unexpected colour or develop an unusual turbidity, repeating the test using a diluted sample with deionized water may be useful.(Dilution of samples is not appropriate for all tests, such as pH).

As an example the API Nitrite Kit is designed to provide accurate results from 0 to 5 ppm (mg/L). Under extreme conditions as high as 25 ppm (mg/L) the Nitrite Test Kit will still show a positive nitrite result but darker than the highest colour on the colour chart. A level of 25 ppm (mg/L) would be very unlikely in a home aquarium or pond and, of course, toxic to fish. Under even more extreme conditions, the API Nitrite Test Kit can be overwhelmed.

As an example I share the following to provide a better understanding of the API Nitrite Test Kit (liquid reagents):

At 0ppm Nitrite the test result reads as 0ppm Nitrite.

At 0.25ppm (mg/L) the test result reads as 0.25ppm (mg/L) Nitrite

At 1.0ppm (mg/L) the test result reads as 1.0ppm (mg/L) Nitrite

At 5.0ppm (mg/L) the test result reads as 5.0ppm (mg/L) Nitrite

At 25ppm (mg/L) Nitrite the test result stays deep purple for 5 minutes. (Note: purple colour is above the 5.0ppm top detection limit of the colour chart provided with the test kit)

At 50ppm (mg/L) Nitrite, the test result turns deep purple initially, but back to light blue after 5 minutes.

At 100ppm (mg/L) Nitrite, the test result turns deep purple initially, but back to light blue after 1.5 minutes.

At 1000ppm (mg/L) Nitrite, the test result turns light blue, never turning purple.

Great to see a big company responding to customers in a genuine way.

Personnally found the API master kit great to use. For the money its well well worth it for anyone even half serious about keeping fish.

Few things I've found though.

The colour increments for low range PH are so similar between 6.6 and 7.2 I really struggle to read it. Luckily my normal tank water it 7.5. Also the 10 and 20ppm Nitrate are very similar. A good improvement would be making the colour change differences more stark. :)