Well grazed algae

I'm going to resist the temptation to be all mysterious about what this is and just tell you. It's an old plastic dustpan which had been left in the yard long enough to collect some water, grow some algae and in due course attract a slug (or slugs) to graze on it. The marks that look like scales are the bald patches of grazed algae - in some places I could clearly see the zigzag path they made that presumably shows how the slug moves its head from side to side in a to munch in a leisurely way while advancing slowly. I spent some time trying to find a way to photograph them without showing the edging of the dustpan before it occurred to me it might actually bring something to the picture. Since this blip and the one for yesterday both involved slugs in some way I'll make sure that tomorrow's doesn't.