No pesticide in the dirt - I use bagged potting soil. It says sterilized but I guess once the bag is open it is no longer sterile. At the end of the day, can anything that lives in potting soil be a threat to fish?
I have little bugs in mine too. Harmless, I think.
I heard of some mites colonizing the white worms cultures often. Not sure if that's what you have. For now I don't have this but probably it is a matter of time. Mine are in the basement where it is cool.
Amazing how much they eat. For now they eat half a slice of bread in a day or 2.