How toxic is ammonium?

[carsona246]

Anyone actually know how toxic ammonium(NH4) is to axolotls? I've been trying to find some info on when it becomes harmful(for instance I know that ammonia is considered harmful at .02 ppm's) but I can't find any info other than ammonium is less toxic than ammonia. Is ammonium more toxic than nitrite, or less toxic? The reason I ask is because after doing some research I found that the majority of what we refer to as ammonia in the hobby is actually NH4, so I thought it wouldn't hurt to skip a few days (I've been doing daily) of water changes on an uncycled tank. My larvae in my ten actually showed signs of stress(gills were pointing forward) when I had less than 1 ppm of ammonia(total ammonia), but according to this free ammonia calculator Ammonia Calculator the levels of NH3 should have been below .02 ppm's and therefore not harmful.
No nitrite to speak of in my tank yet, so I'm just trying to figure out if it was the water movement(got lazy on the top off's), or what could have been the problem. It gills are back to normal after a 50% waterchange so i'm guessing it was the parameters.

 

[Jennewt]

The link you posted is really good, and it seems to come as close as you can get to answering your question (how toxic?). I don't know if an axolotl's sensitivity is the same as a fish's, but it's probably similar. In addition to the overt toxic effect, ammonia and nitrite could also be general stress factors. If you combine a sub-toxic amount of ammonia with other stress factors, and it could still result in illness or death.