What type of bugs? Perhaps adding bug eating bugs will solve the problem as well as offer a way for the substrate to become a living healthy space.....pill bugs and some earth worms are good additions...
Anytime you have damp substrate with "food" particles in it, you are going to have bugs. These bugs are harmless detrivores and nothing needs to be "done" at all. If you just don't like them you can replace, bake or boil your substrate every couple of weeks.
Sir Tom, i have substrate with bugs, i don't know what type or kind of bug it is, small WHITE color bugs. have you ever experienced to have bugs on your substrate.. coco coir. i saw them crawling on my cherry... i soaked my cherry immediately to remove those bugs. is it possible that it may cause problems? parasite/bug bites.