If silverfish have already nested in your home, you'll need to take more extreme measures. However, as a preventative measure, cinnamon is a cheap, effective, and organic option.
To do so, simply sprinkle ground cinnamon around your home. If you don't want cinnamon everywhere, you can use cinnamon essential oil to spread the scent instead.
Alternatively, mix cinnamon oil with your cleaning agent and apply it to silverfish-prone areas. You'll spread that cinnamon aroma while ridding your home of mold and mildew.