OK- got it.
I am familiar with Dr/ Tim's products, his research and his patents. I almost always have a small bottle of his bacteria in the fridge for emergency use. I am going to assume you have the current version of his ammonium chloride. I use this when there is only a small tank involved. I normally am working on a larger scale and mix my own solution from dry ammonium chloride.
I also am in the states and I have no idea if the directions on the bottles in the UK are similar but I am going to assume so. When Dr. Tim originally offered the product it was more concentrated. However that was changed and today the dosing is as follows:
add 1 drop/liter or 4 drops/gallon to produce an
ammonia-nitrogen (
NH3-N) concentration of
2 mg/L-N (2ppm).
or add
1 ml/20 gallons (
75L).
Do not exceed
5 mg/L NH3-N
So the above actually needs to be translated for most of us in the hobby. There are two scales which can be used to measure ammonia/ammonium, nitrite and nitrate. One is favored by science and the other is used mostly in the hobby and the majority of our test kits. The key is in the chemical formulas for the the three things we test.
Ammonia--> NH3 + Ammonium--> NH4 which we measure as Total Ammonia.
Nitrite-->N02
Nitrite-->N03
Notice that all of the formulas start with N, which is nitrogen. And science cares mostly about the N. So their tests only measure the N. Which is why that scale of measurement is called the Nitrogen Scale.
What the above formulas do not show is that the Ammonium, Nitrite and Nitrate are what are called Ions. It means they have either a positive or negative charge. On the other hand ammonia has no charge.
What our test kits do is to measure all of the parts of our trio of nitrogen focused components. Where science only counts the Ns, our test kits also count the H and O parts (Hydrogen and Oxygen). They are measuring the ions as well. And the scale most of our kits use is called the Total Ion Scale.
This is not as complicated as it seems. Just like there are kilometers in the UK and miles in the USA, we can easily convert one to the other. The same is true with the for the Nitrogen and Total Ion scales. At the heart of it is the fact that the test mg/L or ppm numbers are greater when using the Total Ion Scale than they are on the nitrogen scale. And all of this is relevant because the directions on your bottle of ammonium chloride will produce higher numbers on an API test kit.
So, when you add 1 drop per liter and test, you should not see 2 mg/l (2ppm), you should see about 2.56. And when it says not to exceed 5 mg/l-N (5ppm), this would test at about 6.4. The magnification factor increases with each stage in the cycle. BTW, 1 mg/L = 1 ppm.
Armed with the above information and what you posted, here is how it looks to me.
While your tank is called a 125L, you do not have that much water in it. I would bet the tank is not filled to the very top, there is likely some air space. Then the substrate and any decor also displace some of the volume. The more things we put into a tank, the lower the potential water volume gets. So lets assume your tank really has only 90% of that 125L or 112 (rounded down).
So to produce Dr. T's 2 mg/l-N or API's test kit result of 2.5 mg/L, you should have added 112 drops (about 1.5 ml) of ammonium chloride not 25. 25 drops should only create about 22% of 2.5 mg/L, or about .5 mg/L of ammonia on an API kit. (On Dr. T's Nitrogen scale that would have been .44 mg/L-N) So, I have no clue how you got to 2 ppm on your test kit. I see any of several potential explanations:
1. Your test kits, or at least the ammonia one is expired.
2. You are doing the testing incorrectly.
3. You are misreading the test result color.
3. You could have something in the tap water which gives false readings for ammonia. Iron would be one such thing.
4. You have ammonia in your tap water.
I also have a few more Qs.
What dechlor are you using?
Can you please confirm that you are using API test kits and they are not expired. If not API, then what brand?
Do you have test numbers for your tap parameters?
I am thinking that your solution is to do one of two things. Both require a reset of the tank (i.e. several large water changes). Then you will start over. One way is to do a traditional fishless cycle with no added bacteria. For that you should follow thie directions on this site for doing that. This would mean about 4 -6 weeks to cycle the tank.
https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/
If you are in a rush, then you need to use the Dr. Tom's and to follow his instructions for doing a fishless cycle using his ammonium chloride and his bacterial starter.
https://www.drtimsaquatics.com/resources/library/quick-guide-to-fishless-cycling-with-one-and-only/
I am happy to work with you to get your tank cycled either way if you want my help.
