I don’t see any other way to know for sure. I wish there were another way. But using feeder fish seems the most ethical path.I can easily adapt guppies to saltwater fairly quickly. They would work - I still expect an ethical complaint from people here - I'm receiving my Seachem multi-tests tomorrow. I'm going to approach it a little differently that @Dan_P
I am very interested in these results. And like you, I have no clue whether prime actually detoxifies ammonia.