Hello! I brought in a houseplant that apparently had some fungus gnats in the substrate, and they've spread to my terrestrial frog enclosures. How do I get rid of them without harming my frogs? Is it as simple as replacing the substrate? How do I prevent re-infestation with the new substrate? The stuff I've read online says to keep the substrate dry or put a layer of sand over the top, neither of which will work here for obvious reasons.