I have no idea what the stuff stuck to it is, but by your description it sounds like an Ozzy Washer... The microbials are in the Ozzy pad that needs regular servicing.. They arrive as unhatched microbials, the heat from the ozzy washer hatches them & if you shut the heat off they die.... And trust me they stink when they die... You also need to use Ozzy Juice in the tank to support their ecosystem.. They eat the oil & grease...