total ammonia or free ammonia?

[joeguzdial]

my test kit measures both total and free ammonia. Which of these should i be testing and what is the difference between the two. thanks in advance.

 

[littlemannin]

are the bottles labeled NH3 and NH4? or are they separate bottles? I think there may be a chart that came with it to figure it out depending on PH and temp

 

[Recife]

free ammonia is the more toxic type, but you still want to be free of both, so make sure your total ammonia is 0 too.