CSJ has never recommended that mold or mildew be allow to grow in the crabitat. It has always been our stance that this is not safe for a hermit crab’s gills. While they may encounter decaying, rotting matter on the beach they are also in open air where the mold spores naturally dissipate. This is not the case in a closed environment.
One Facebook HC community encourages members to let mold grow unchecked in the crabitat. Insisting it’s safe and beneficial.
Last month I contacted a group of invertebrate veterinarians about this issue. They confirmed that there is no research on this topic. However, they advised there is no way to know if the mold growing is beneficial or harmful and therefore should be avoided.