JT Eaton's Boric Acid Insecticidal Dust
For a reliable and time-tested silverfish killer, J.T. Eaton Answer Boric Acid Insecticidal Dust has proven results for decades. Boric acid is one of the standard silverfish killers. When sprinkled where silverfish are known to congregate, the particles are abrasive to the exoskeleton both inside and out. It also acts much like borate powder in that it doesn't allow proper digestion of food, literally starving and dehydrating a silverfish to death. It is relatively safe to use, but always wear gloves when broadcasting the powder, and never inhale it as you go. It is simple to spread and effective, and has a proven track record that is the standard for silverfish elimination.