Ammonia Testing

I think all the home testing kits use the salicylate test, so they have the same colour change. The yellow of 0 and the greenish tinge of 0.25 can be very hard to distinguish. The light it is read under can affect the apparent colour with fluorescent lights (tubes or compact fluorescent bulbs) being the worst for this.


Ammonia exists in 2 forms in water - toxic ammonia and less toxic ammonium. The amount that it is each form depends on both pH and temperature. Luckily there are on-line calculators to work it out for you.
https://www.hamzasreef.com/Contents/Calculators/FreeAmmonia.php
In the left box, set salinity to zero, then enter your readings for ammonia and pH, and the tank temp, then click calculate. You want the number in the bottom box on the right hand side. I would use 0.25 for ammonia, as you can't decide between 0 and 0.25.
As long as that number is below 0.02, the fish are safe. Especially as your ammonia reading is not right on the 0.25 green.

But whenever that number from the calculator goes over 0.02, do a water change.

0.0058 

The ammonia in tap water usually comes from chloramine. Some water companies use this instead of chlorine to disinfect the mains water. Chloramine is an ammonia and a chlorine joined together; our dechlorinators split it up to chlorine and ammonia then remove the chlorine part leaving the ammonia part still in the water. This is why so many dechlorinators also contain something to detoxify ammonia albeit temporarily, but by the time this ammonia becomes toxic again, the filter bacteria have already 'eaten' it.

I can't remember whether our ammonia test kits detect the ammonia half of chloramine though