Roach poisons may use a number of different active ingredients, but two of the most common are Hydramethylnon and Fipronil. Hydramethylnon is more thorough, contaminating the bodily fluids of any roach that consumes it to ensure that the poison spreads throughout the colony. Fipronil is less thorough but works faster.
Poisons containing Hydramethylnon usually take around seven days to show results and are recommended for very large or serious infestations. With Fipronil, users begin to see results within hours. It works best for smaller surface infestations. Poisons containing both types of ingredients are available in crystal, gel and trap form.