Oh goodness! This reminds me of the guppies I used to own. They didn't like what I was feeding them and turned to cannibalism by attempting to chew off one another's tails. The survivors in their last moments would have these cottony things stuck to their tails before eventually meeting their maker.
This cottony mold just brings back a lot of guilt from a negligent aquarium owner.
Wait a minute.
The mouse went to eat your food which was left out in the open.
Then the dish went into the microwave and all kena cooked together.
Then wife forgot to take out (at least a few days), and mould grew.
Tio boh?