They added boric acid and pheromone blockers to the gel bait. After the cockroaches are poisoned, signals for dehydration show up in both their bodies and nervous systems.
So as they're being poisoned, their instincts drive them to flee toward the sewer, so they won't die inside the house or out in the open.
The sewer is for waste anyway, so you don't have to worry about contaminating the water supply.
With Xu Yun's assurance in place, Xiao Rong couldn't sit still anymore and quickly had Xu Yun put gel bait in all four corners of the kitchen.
Once everything was set.
Xiao Rong straightened his expression a bit, then led Xu Yun and Gu Qunqing back to the living room, and said:
"Xu, Qunqing, did you come over today because you saw my Moments post the other day and just wanted to get some stuff for free?"
Xu Yun smiled and nodded, saying:
"That's certainly part of it, but it's not like we're here just to hold you to your promise."
