Finding the Problem with ACO Ammonia Test Strips

[modified lung]

I recently bought some Aquarium Co-op test strips. A few people on the forum have been having problems with the ammonia strips. I've been a water quality analyst for quite a few years now—previously at a research lab for fish conservation and now at a large network of fish farms. In that time I've done a lot of experimenting with the different test kits I've been provided. So I thought I'd try to figure out why people are having problems with these strips.

Before we can gauge their accuracy, we need to know what exactly the ACO ammonia test strips are testing. There are multiple types of ammonia—ammonia (NH3), ammonium (NH4+), and total ammonia (TA or NH3/NH4+) which is the total amount of NH3 and NH4+ combined. NH3 is also often referred to as "unionized ammonia" or "free ammonia" to more clearly differentiate it from the other forms. Some tests only report the nitrogen in ammonia (NH3-N, NH4-N, total ammonia-nitrogen/TAN) but the difference isn't very significant at low levels (1.0 ppm NH3-N = 1.2 ppm NH3).  

The ACO test strip bottle is labeled "Ammonia Test Strips". If we take the label literally, we might believe the strips test for NH3. However, this is hard to trust because many test kits, especially for the aquarium hobby, aren't very clear about what exactly is being tested.

Turning the label around, NH3 would not make sense with the color scale given on the back of the label. For example, I would think the "caution" level for NH3 would be considered closer to 0.02 ppm which is far lower than the 0.5 listed on the label. Not to mention 0.5 ppm NH3 would kill many fish in a couple days which I personally would label as "change water" instead. Here's the ACO ammonia strip color chart next to an example of a NH3 color chart that does make sense:

However, the ACO color chart does make sense if the strips are instead testing for TA or for NH4+. For reference, the API ammonia liquid test kit measures TA. And the API color chart is very similar to the ACO chart.

 

How Different Types of Test Strips Work

If you're not interested in how ammonia test strips work, feel free to skip to the "Experiment" section of this post.

 

Generally, test strips that measure TA or TAN have two pads. Notice the front labels of both these test strips say "ammonia". However, the back label of the HACH Aquachek ammonia strips specify that TAN is being tested while the ACO back label still only says "ammonia" (HACH is a company that makes highly accurate, scientific grade water quality test kits) Here's a photo of HACH ammonia test strips next to the ACO ammonia test strips:

A lot of people here already know that the amount of NH3 and NH4+ in a water sample depends on the pH. Higher pH means more NH3. Lower pH means more NH4+.

The large pad on the HACH strip increases the pH of the water sample to 10 in order to convert all of the NH4+ to NH3. The small pad then measures the NH3. To work properly this requires the water sample to be a specific volume. In this case the HACH instructions specify that each water sample should only be 3 milliliter or the result may not be accurate.

The API liquid ammonia test kit works in a very similar way. The bottle #1 reagent increases the pH and the bottle #2 reagent measures the NH3.

ACO strip instructions don't mention a specific volume of water is necessary. In fact, videos made by ACO themselves show their strips being dipped into a 1 or 2 liter container of water and even straight into a large-ish fish tank. This would mean no pH change is required for the strips to work.

I confirmed the HACH strip alters the pH by placing a whole strip into some 7.0 pH calibration solution and measuring the pH increase. The pH only rose to 8.0 because the volume of calibration solution was more than 3 milliliters. I did the same with an ACO strip and no change in pH was observed. 

But ACO strips don't need to change the pH if they were meant to measure only either NH3 or NH4+. This is only necessary if the strips are meant to measure TA.

Taking all of this into consideration, I'm guessing the ACO ammonia strips are actually testing for NH4+. This would make a lot of sense because the strip might only need one pad and in most normal cases NH4+ is close enough to TA to use the same color charts.

 

Experiment 

First, I tested a sample using both a HACH Aquachek ammonia strips and a HACH liquid test vial read with a HACH spectrometer.

For test strips (and liquid tests as well), keep in mind the results rarely look exactly like the color charts because of a number of factors that influence the speed and intensity of the color change. Temperature and light are two examples. This means, if you want a high degree of accuracy, you have to develop an eye for interpreting the results with your testing conditions and habits. Of course this isn't easy unless you have tests from known concentrations to compare with your results. But for knowing if your aquarium is in a safe general range, this isn't terribly necessary.

In developing an eye for HACH strips I've learned to pay more attention to the amount of yellow that fades than the shade of green that develops. I would interpret my HACH strip results as 0.8 or 0.9 ppm TAN. The liquid test vial and spectrometer showed 1.16 ppm TAN. Close enough for a strip.

Next, I took part of the water sample and some baking soda until the pH rose to 8.1 just to see if there will be any noticeable difference.

Lastly, I took another part of the original sample and added enough ammonium chloride to bring the TAN up to about 200 ppm. Unfortunately, I don't have a test that can measure such a high amount of TA. But we shouldn't need to because all we need to see with this sample is if the strip results read within the range of the kits or off the charts.

Here are the possible results we should expect depending on what the ACO strips are measuring (the amount of NH4+ is a little higher than the TA because of the extra H compared to NH3):

	Original	+ Baking Soda	+ Ammonium Chloride
pH	7.3	8.1	7.3
TAN	1.2 ppm	1.2 ppm	~200 ppm
TA	1.4 ppm	1.4 ppm	~240 ppm
NH3	0.02 ppm	0.10 ppm	~2.7 ppm
NH4+	1.5 ppm	1.4 ppm	~255 ppm

 

Results

Here are the ACO test results for for the original water sample (left) and the sample brought to pH 8.1 (right).  The two results look almost the same: 0.5 ppm:

This might look like an unexpected result but we should first know that all water quality tests have a range of accuracy. For ammonia tests that range is usually above 0.25 ppm. That means to the human eye even trace amounts of ammonia will look almost exactly like 0.25 ppm on the color chart.

For example, in the past I've compared the results from the API liquid ammonia test kit with HACH liquid test vials read with a spectrometer. I found that even readings around 0.02 ppm TA with the liquid vials and spectrometer looked exactly like 0.25 ppm TA on the API color chart. But given that 0.5 ppm is the next color after 0 ppm on the ACO ammonia strip color chart, the range of accuracy for this test is probably above 0.5 ppm instead of 0.25 ppm. That means these do show one of the possible expected results: between 0 and 0.5 ppm.

But that's not all. I said they "almost" look the same. Notice the more yellow ring around the edges of the pad on the right? On some strips that means a slightly lower concentration was measured. Although, I haven't used the ACO strips for long enough to be certain if this is the case here. 

Either way, these results don't make sense if the ACO strips are measuring TA or NH4+. They would, however, make sense if the strips were measuring only NH3. 

 

Here are the results of the sample + ammonia chloride with the HACH and ACO strips:

As you can see the HACH strips read off the charts which is expected if they measure TAN. The ACO strip reads I'd say somewhere around 2.0 or 3.0 ppm. The ACO strips again line up with the expected NH3.

But that's not all.

Interestingly, when using an ACO strip on a 3 milliliter water sample that was already tested by a HACH strip, the ACO results showed the correct amount of TA (1.2 ppm) instead. Remember, the large pad on the HACH strip increases the pH to 10 in order to convert all of the TA to NH3. My pH meter isn't small enough to fit into 3 milliliter so I couldn't confirm the pH was at 10. But I was able to confirm the large pads do increase pH in a larger volume sample, so I trust the HACH strips work as described. Here's a picture of another ACO strip used on the original sample (left) next the a strip used on a sample exposed to a large HACH pH altering pad:

 

Conclusion

That's at least 3 points of evidence that ACO ammonia test strips only measures unionized ammonia (NH3).

Each part of the experiment I described above was repeated at least 3 times with water from 3 different sources each with 3 different concentrations of TA. The results all lined up with ACO strips measuring NH3 …and very accurately I might add. I was easily able to distinguish between 0.8 and 1.2 ppm. Far, far more easily than with the expensive HACH strips. That's extremely impressive. And extremely useful for applications where NH3 doesn't need to be so low.

So this might not be such a big deal …the Seachem Ammonia Alert cards only measure NH3 for example. But the Seachem cards have a color chart that makes sense for the typical levels of NH3 that might be found in an aquarium …while the ACO ammonia strips do not. Unfortunately, that makes the ACO ammonia strips not very useful for most aquarium applications, especially if the range of accuracy is indeed above 0.5 ppm.

 

Edit: I've confirmed the range of accuracy seems to be above 0.5 ppm NH3. In testing my blackwater tank with a pH of 5.5, the ACO strip showed 0.5 while other tests including TA tests showed 0. Although the ACO pad did again have the yellow ring around the edges that I mentioned earlier. (For reference, at pH 5.5 there would only be 0.0002 ppm NH3 for every 1.0 ppm TA.)

----------------

This is kind of awkward. It seems a lot of people on here have had problems with the ACO ammonia strips. I was hoping if I bought some, I could find what was being done wrong. But I think people are in fact using them correctly. The strips are just measuring something very different (NH3) than what I think is reasonable for them to believe (TA).

I mentioned these are still useful for some applications. I plan on using them for my many greenwater cultures. I sometimes add high amounts of NH3 to them. I've been looking for a quick, cheap way to test if the greenwater has consumed enough NH3 to be safely dumped into my other live feed cultures (daphnia, moina, etc.). These ACO ammonia test strips will work great for this, especially since they can be cut in half without affecting their accuracy.

 

Edited September 4, 2022 by modified lung
New paragraph near end

[redfish]

Very interesting work.  Thanks for sharing.

[eatyourpeas]

Yes, great report! Thank you!🙂

[Tomdobbins]

Myself I love many of the aquarium coop cory brand items...food....fertilizer...the strips seem inaccurate when I use them...I asked one time...said they worked fine....well well...Back to API I guess.... !!!STILL LOVE THE FERTILIZER AND FOOD CORY SIR!!!

[Cleveland M]

I have lots of equipment/supplies from ACO and and will get more but, after reading this I guess this is one item I won't get from Cory.

Thanks for putting in the work for us.

[modified lung]

On 9/3/2022 at 2:29 AM, Tomdobbins said:

Myself I love many of the aquarium coop cory brand items...food....fertilizer...the strips seem inaccurate when I use them...I asked one time...said they worked fine....well well...Back to API I guess.... !!!STILL LOVE THE FERTILIZER AND FOOD CORY SIR!!!

 

On 9/3/2022 at 5:24 AM, Cleveland M said:

I have lots of equipment/supplies from ACO and and will get more but, after reading this I guess this is one item I won't get from Cory.

Thanks for putting in the work for us.

I think ACO products are some of the best out there. And so far I'm finding the Multi-test Strips to be crazy accuracy. 

I'm wondering if the manufacturer screwed up this batch of ammonia strips or if there was a miscommunication when developing them. Aquarium hobbyists tend to refer to all forms of ammonia as just ammonia. Honestly, I do it too. Ask for an ammonia test strip and that's exactly what was made.

Unless I missed something but it all lined up so perfectly and consistently with unionized ammonia.

@Cory would probably want to know.

 

[Cory]

I'll inquire with our manufacturer.

[Kiefer]

I was under the impression that it was known that ACO test strips only measured NH3 and not total ammonia, for whatever reason I recall this being mentioned on a stream at some point, I discovered it on my own in my adventures with ADA aquasoils. I think there is a reasonable argument for strips that do that (and I personally prefer that to the API total ammonia test for practical reasons), though it would be good to have messaging on or associated with the product that explains this.

If you're measuring total ammonia you need to provide a pH chart and have the user test pH to give good guidance on what is actively harmful. But that entire discussion veers off into nerd territory that most people don't need to care about. For all it really matters IMO the strips could say "+" or "-" and the utility would be about the same at least for me.

[modified lung]

On 9/3/2022 at 1:08 PM, Kiefer said:

I was under the impression that it was known that ACO test strips only measured NH3 

It's mostly that the color chart doesn't make a lot of sense for NH3 in aquariums. For example, the lethal concentration of NH3 for many fish is only 1.0 ppm NH3. For cardinal tetras the 96 hour LC50 is 0.3 ppm NH3 to give an extreme example. It doesn't make much sense to water change at or above the LC like the chart suggests. You'd want to do it far, far below that. I've seen guppies have problems with < 0.1 ppm NH3.

The chart definitely makes sense for total ammonia though. And looks exactly like the charts in on other kits that measure total ammonia but also just say "ammonia" on the front label. That's why I assumed they weren't meant to measure NH3.

On 9/3/2022 at 1:08 PM, Kiefer said:

I think there is a reasonable argument for strips that do that (and I personally prefer that to the API total ammonia test for practical reasons), though it would be good to have messaging on or associated with the product that explains this.

I completely agree. I'd love a NH3 strip with a measurement range more like the Seachem ammonia alert cards. I've noticed the Seachem cards also have a bad reputation because people also assume they measuring total ammonia. I think if the product labels clearly said "unionized" or "free ammonia" instead of just "ammonia", they'd get a lot less complaints.

On 9/3/2022 at 1:08 PM, Kiefer said:

If you're measuring total ammonia you need to provide a pH chart and have the user test pH to give good guidance on what is actively harmful.

I think we're usually just given rules of thumb that assume high pH which is fine IMO.

On 9/3/2022 at 1:08 PM, Kiefer said:

For all it really matters IMO the strips could say "+" or "-" and the utility would be about the same at least for me.

Personally, I think it's a mistake for these companies to assign specific numbers to color changes. If they gave ranges instead people might not expect an unreasonable amount of accuracy.

Edited September 3, 2022 by modified lung

[face]

interesting read thanks. testing ammonia at the best of times is hard to do accurately it seems, trying to do it with a small strip cheap and simply without accounting for ph temp or the dozen other thing that can interfere is likely impossible.

[Tomdobbins]

On 9/3/2022 at 5:24 AM, Cleveland M said:

I have lots of equipment/supplies from ACO and and will get more but, after reading this I guess this is one item I won't get from Cory.

Thanks for putting in the work for us.

YES....after in store they told they are fine...when they are not working...  ohh well....almost time to order more FERT!!!!!

[modified lung]

On 9/3/2022 at 4:03 PM, Tomdobbins said:

YES....after in store they told they are fine...when they are not working...  ohh well....almost time to order more FERT!!!!!

Technically, they do work fine ...they work really, really well for their range of accuracy actually. There just seems to be a lot of miscommunication over what the strips are actually testing which I'm not sure they realize.

Edited September 3, 2022 by modified lung

[Tomdobbins]

What is YOUR FAVORITE fish food.... ME?...my fish look great with the bug bites color enhancing pellets

[Anjum]

On 9/3/2022 at 4:35 PM, modified lung said:

Technically, they do work fine ...they work really, really well for their range of accuracy actually. There just seems to be a lot of miscommunication over what the strips are actually testing which I'm not sure they realize.

I'm a novice in studying aquarium chemistry, so correct me if I'm wrong.. but if I'm understanding correctly, NH3 is what's toxic in smaller amounts. NH4 isn't toxic until higher amounts. So isn't it more useful (for aquarium keeping) to know what the NH3 level is alone? Wouldn't a total NH3+NH4 level be sort of ambiguous or arbitrary, not knowing specifically what the ratio is? 

[Odd Duck]

On 9/3/2022 at 10:22 PM, Anjum said:

I'm a novice in studying aquarium chemistry, so correct me if I'm wrong.. but if I'm understanding correctly, NH3 is what's toxic in smaller amounts. NH4 isn't toxic until higher amounts. So isn't it more useful (for aquarium keeping) to know what the NH3 level is alone? Wouldn't a total NH3+NH4 level be sort of ambiguous or arbitrary, not knowing specifically what the ratio is? 

Depends on the pH of your tank water, among other things.  My tap runs about 8.4.  Tanks run a bit lower since I mix in RO and run pretty heavily planted.

[modified lung]

On 9/3/2022 at 8:22 PM, Anjum said:

I'm a novice in studying aquarium chemistry, so correct me if I'm wrong.. but if I'm understanding correctly, NH3 is what's toxic in smaller amounts. NH4 isn't toxic until higher amounts. So isn't it more useful (for aquarium keeping) to know what the NH3 level is alone? Wouldn't a total NH3+NH4 level be sort of ambiguous or arbitrary, not knowing specifically what the ratio is? 

You're right about all of that. What's odd about the ACO strips is the color chart. The same exact alert scale is used on NH3+NH4 tests. That's why some people assume the ACO strips test for NH3+NH4.

[face]

On 9/3/2022 at 11:22 PM, Anjum said:

I'm a novice in studying aquarium chemistry, so correct me if I'm wrong.. but if I'm understanding correctly, NH3 is what's toxic in smaller amounts. NH4 isn't toxic until higher amounts. So isn't it more useful (for aquarium keeping) to know what the NH3 level is alone? Wouldn't a total NH3+NH4 level be sort of ambiguous or arbitrary, not knowing specifically what the ratio is? 

the problem with NH3 tests is they need to be more accurate and ph isn't the most stable thing in the world its not uncommon for an aquarium to have a 1ph change so you can have safe levels sometimes and unannounced to you toxic levels at others, a total ammonia test is more likely to warn you something is happening in my opinion any ways.

[nabokovfan87]

On 9/2/2022 at 6:34 PM, modified lung said:

In developing an eye for HACH strips I've learned to pay more attention to the amount of yellow that fades than the shade of green that develops.

This is a huge tip for people who struggle to read test strips!  Find out what the color shifts are and then focus on that mindset.  I have always had trouble with some ranges, but trying to decipher the code using the above tip is one of the best mental methods to try to remove my own subjectivity and skewing colors.  Eyes can play tricks on you, or at least I feel like mine are whenever I am testing things.

 

On 9/3/2022 at 9:18 PM, modified lung said:

You're right about all of that. What's odd about the ACO strips is the color chart. The same exact alert scale is used on NH3+NH4 tests. That's why some people assume the ACO strips test for NH3+NH4.

Some strips have the same chart, but have different directions.  When I was trying to help answer this question for someone here on the forums I looked up the other common ones and they had the FAQ post on their website, same scale, etc, and it all claimed to test for TA.

The real question for me as someone trying not to screw up results, is why one test says dip for 10 seconds, another says 30, etc.  I am not trying to think that one test is better than the other, but I have always had nitrite show up, and almost never had ammonia show up.
 

On 9/2/2022 at 6:34 PM, modified lung said:

But that's not all. I said they "almost" look the same. Notice the more yellow ring around the edges of the pad on the right? On some strips that means a slightly lower concentration was measured. Although, I haven't used the ACO strips for long enough to be certain if this is the case here.

could this just be due to time out of the water and the pad "puffing up" with some pads having a variation in how they do that? Meaning, the yellow outline is some aspect of the middle region of the pad that isn't colored?  I would imagine the whole pad would change color and react, but that's moreso a question for your area of experience and expertise!

[Guppysnail]

Ok so bear with me. I have ZERO chemistry knowledge but love to learn.
 

I don’t know the difference between the two Nh 3-4  would you mind explaining so I can learn? I may or may not be the only one this inept at chemistry 🤣

The  seachem ammonia alert measures only the really harmful ammonia?

The test strips measure one or both? But potentially has the wrong color chart? 
 

What is the api liquid measuring?

 

Sorry for simplistic questions but not understanding chemistry made it hard for me to comprehend your great info. 
 

Thank you 🤗

Edited September 4, 2022 by Guppysnail

[modified lung]

On 9/4/2022 at 5:34 AM, Guppysnail said:

.

On 9/3/2022 at 9:59 PM, face said:

the problem with NH3 tests is they need to be more accurate and ph isn't the most stable

 

On 9/4/2022 at 4:23 AM, Pepere said:

and as others mentioned ph changes a fair amount through the course of the day both with co2 supplemented tanks and low tech tanks.

These are good points I forgot to mention. I had thought about this for testing my greenwater cultures. Microalgae consumes KH and the pH can be anywhere between 6 and 9 so the amount of NH3 in the greenwater jar may not be the amount of NH3 I'm adding to the Moina jar when feeding. I think it will work out though.

On 9/3/2022 at 10:27 PM, nabokovfan87 said:

The real question for me as someone trying not to screw up results, is why one test says dip for 10 seconds, another says 30, etc.  I am not trying to think that one test is better than the other, but I have always had nitrite show up, and almost never had ammonia show up.

Really you can wait any amount of time and make a calibration curve based on the colors that develop with different concentrations for that same amount of time.

I don't know if this is true of all tests, but I've noticed the longer the test wants you to wait, the more stable the color becomes. Tests with a 30 second wait have to be read right away or their color changes. Tests with a 20 minute wait can sit around for a day and still be about the same color.

You could say the 20 minute test is better but when I'm at home I'm impatient and would rather wait 30 seconds even if there's a bigger margin for error. I just have to not be too lazy to set a timer ...again.

If you mean after your cycle should already be established, nitrite-oxidizing bacteria are a lot more sensitive to basically everything compared the ammonia-oxidizing bacteria. That could be why you have nitrite show up but never ammonia.

On 9/4/2022 at 5:34 AM, Guppysnail said:

I don’t know the difference between the two Nh 3-4  would you mind explaining so I can learn?

Ammonia (NH3) = N-H-H-H

Ammonium (NH4+) = N-H-H-H-H

pH is determined by how much free H+ (hydrogen ions) is in the water ("free" means it's not attached to anything else, it's just by itself).

Lower pH means there's more free H+.

When there's a lot of free H+ flying around, some of it attaches to NH3 which turns it into NH4+. That's why there's less NH3 at low pH.

The extra H in ammonium gives it a positive charge (+) which makes it less toxic because that makes it more difficult to be absorbed into a fish's bloodstream. 

The lethal concentration (LC) of ammonia (NH3) is usually somewhere between 1 and 3 ppm over 2 or 3 days of exposure. The lowest fish LC I know of is for cardinal tetras which is between 0.3 and 0.4 ppm over 4 days of exposure.

The LC of ammonium (NH4+) is usually around 40 to 50 ppm.

I hope that all made sense.

On 9/4/2022 at 5:34 AM, Guppysnail said:

The  seachem ammonia alert measures only the really harmful ammonia?

The test strips measure one or both? But potentially has the wrong color chart? 
 

What is the api liquid measuring?

The Seachem alert card measures ammonia (NH3) which is the more toxic form.

The ACO test strips seem to also measure ammonia (NH3). The color chart on the bottle says water change at 1.0 ppm which is above the lethal concentration of NH3 for some fish. (This is why I'm wondering if the manufacturer made a mistake with either the type of test ACO wanted or with the chart.)

The API liquid test kit measures both NH3 and NH4+ combined which is called "total ammonia" or "NH3/NH4+".

On 9/4/2022 at 5:34 AM, Guppysnail said:

Sorry for simplistic questions but not understanding chemistry made it hard for me to comprehend your great info. 

No problem. It's hard for me to find a balance between explaining stuff and long winded-ness.

[Guppysnail]

@modified lung thank you for this explanation. Now I also understand why ammonia is more toxic at higher ph. I really appreciate your time and all you put into this article. 

[modified lung]

On 9/4/2022 at 7:53 AM, Guppysnail said:

@modified lung thank you for this explanation. Now I also understand why ammonia is more toxic at higher ph. I really appreciate your time and all you put into this article. 

Just trying to cull the existential boredom.  👍

[modified lung]

On 9/4/2022 at 8:31 AM, Pepere said:

@modified lung, Am I correct in thinking that if I take a sample of water with total ammonia of 1 ppm and raise the ph of the sample to 10, then the Aquarium Co op ammonia test strip should read a similar result as all of the ammonium would be converted to NH3 and hence readcout as total ammonia?

That's exactly what I did and exactly what happened. The reading on the ACO strip was crazy accurate too. Like the best strip I've ever seen.

[Kiefer]

On 9/3/2022 at 3:29 PM, Pepere said:

Sure, but if that is the case the detected range for free ammonia needs to be a whole heck of a lot lower than starting at 0.5 ppm free ammonia which is highly toxic to fish.

Depends how we define highly. 0.5ppm free ammonia is where most aquaculture studies I've read say you start seeing hazards from chronic exposure. So if your aquarium spikes to 0.5 and you do something about it quickly there's not that much of a problem with it, if it was from a one-off event like a fish dying or a kid dumping a container of food in. If you're sitting at 0.5 for days or weeks on end you are going to start seeing damage build up. But if your aquarium spikes to 1, or 2ppm, you need to do something or you could wake up to dying fish.

But that varies quite a bit based on species. Pond/lake dwelling species can be a lot hardier, one study I vaguely recall showed that for tilapia, the king of garbage water fish, chronic damage didn't start until almost 2ppm free ammonia which is acutely toxic to many other fish, and I am all sure we have seen of or heard about a goldfish living for 5 or 10 years in a toxic nitrogen soup. Then you have fish that mostly live in acidic riparian systems where free ammonia basically can't exist like cardinal tetras who start showing chronic damage at 0.1ppm, and the same is true for many saltwater fish (and exacerbated by the fact that saltwater pH is inherently high so you don't get much help from ionization).

I guess it also depends how you interpret "caution." Me? I see caution and read "Do something." For other people, especially if you're busy with kids or whatever I can totally see people reading that caution as "Do something about it this weekend." Which probably wouldn't kill most fish at 0.5ppm, but could easily kill fish at 1 or 2ppm.

ANY ammonia level should be 'caution' in terms of your filter not being sufficient/stocking too high, even though it might not be acutely or even chronically hazardous to the fish at persistent but low levels. But it's hard to put all of that information on the back of a bottle especially when you can't get most people to read one or two lines these days.

[nabokovfan87]

On 9/4/2022 at 7:23 AM, modified lung said:

On 9/4/2022 at 5:34 AM, Guppysnail said:

I don’t know the difference between the two Nh 3-4  would you mind explaining so I can learn?

Ammonia (NH3) = N-H-H-H

Ammonium (NH4+) = N-H-H-H-H

pH is determined by how much free H+ (hydrogen ions) is in the water ("free" means it's not attached to anything else, it's just by itself).

Lower pH means there's more free H+.

When there's a lot of free H+ flying around, some of it attaches to NH3 which turns it into NH4+. That's why there's less NH3 at low pH.

The extra H in ammonium gives it a positive charge (+) which makes it less toxic because that makes it more difficult to be absorbed into a fish's bloodstream. 

The lethal concentration (LC) of ammonia (NH3) is usually somewhere between 1 and 3 ppm over 2 or 3 days of exposure. The lowest fish LC I know of is for cardinal tetras which is between 0.3 and 0.4 ppm over 4 days of exposure.

The LC of ammonium (NH4+) is usually around 40 to 50 ppm.

I hope that all made sense.

I totally enjoyed reading this and the explanation.  Much appreciated.  Things like this help us all to really understand what is going on in the tanks chemically or biologically with all these microscopic bits going on.

On 9/4/2022 at 7:23 AM, modified lung said:

You could say the 20 minute test is better but when I'm at home I'm impatient and would rather wait 30 seconds even if there's a bigger margin for error. I just have to not be too lazy to set a timer ...again.

If you mean after your cycle should already be established, nitrite-oxidizing bacteria are a lot more sensitive to basically everything compared the ammonia-oxidizing bacteria. That could be why you have nitrite show up but never ammonia.

I figured this was why.... my correlation being that the first part of cycling a tank is very easy to get going, but going from nitrite into nitrate takes a little bit of time.  Thank you for the clarification!