Prime contains hydrosulphide salts, this is a reducing agent. That's why it reacts with chlorine compounds, which are oxidising agents. If there is no chlorine compounds left in the aquarium water, it will find something else to reduce (oxygen in the water), and thus will break down. It even says on the bottle you can use a 5X dose in emergencies. Just boost the circulation / aeration rate as it is an oxygen scavenger and will consume O2 on excess use.
Burt
Burt
