Yeah, exposing them to the air for a couple minutes. They have water in them from the shipping, so sometimes if they’ve been in the bag for a long time (a particularly long trip) I’ll just see if they’ll spit out some of that nastier water before putting them in.
Good question. For me it’s less of an ammonia thing and more of a visual thing. Every once in a while I’ll get a batch of nems that have more sediment or “gunk” in the water.
I’ve collected them for over 20 years, and sometimes I choose to keep them in the net for 3-5 minutes when I drain the water from the bag. This just gives them a chance to expel any of that gunk/algae/water if the water was a little more dirty.
It also gives me an additional chance to check for any damage to the feet or any signs of bacterial infection.