It's amazing how tolerant triops are of ammonia, though do note, that most triops tanks are have fairly acidic water so most of the ammonia is actually in it's non-toxic ammonium form.
For triops tanks I like to use box filters with zeolite and carbon in them, this keeps the water ammonia and toxin free until a decent bacterial colony grows on the media for the adult triops. Mulm from mature aquarium filters is great too.