Dilution Question

[Attreui]

I'm a bit confused. I am curing some more live rock in a 50 gal tub with a filter and powerheads. I got my ammonia spike which was about 4-5ppm. I just did a water change of 75% with freshly made saltwater (for giggles I tested it and was 0ppm) and the ammonia is still around the same. Doesn't that violate some law of chemistry?? I would think the dilution would at least halve the amount of ammonia in the water. Am I missing something?

Thanks!

[Randy Holmes-Farley]

It is likely a combination of new ammonia produced and testing inaccuracy that makes it look as if it didn't decline. I assume the test shows no ammonia in the new water before mixing?