If you let the substrate dry out between watering you probably wont encounter mold very often. If you have a sp that needs to stay moist all the time, you can turn loose some Isopods in the tank. I do that with all my moist species.
It'll work if you get it all but you need to keep your eye on it and see if anything else pops up. Remove it if it does otherwise, in a couple of days goes by and nothing pops up then you know you got it all.
Scrape out the mold and let the substrate dry out more. Ts can have a little mold and just scrape it out, but if a lot of it starts growing, you need to change to a new container with substrate kept drier.