If you can remove it from the tank, then remove it, put paper towels in sink, sit the DW on them, pour Hydrogen Peroxide 3% over the fungus on the DW, then lay the Peroxide drenched paper towels over the DW and leave them sit on it for 20 minutes. Then just put the DW back in the tank and don't rinse it. The Peroxide won't hurt anything in the tank.