Fungus and mold is harmless and usually no reason to change the substrate unless it takes over. What kind of substrate are you using? That looks very dark. A. geniculata only needs a little bit of moisture.
@boina Previously I was using coconut fiber. Now I am trying out Lucky Reptile Jungle Bedding for her and some others tarantulas. I have only watered the sphagnum moss, though not completely. The substrate itself is pretty dark on its own, even when completely dry.
But your statement about fungus and mold being harmless surprises me now tbh. Isnt mold like a big no go in tarantula enclosures? :O
@Aestas The dangers of mold and fungus are vastly overestimated. I've mold in several enclosures. I've added more springtails but other than that I ignore it. This is not a fringe opinion but based on the biology of tarantulas and shared by many of the more experienced keepers. A healthy tarantula is not harmed by fungus.