I do clean my aquarium. I really do. I scrub the walls every week with a toothbrush and a green dish scrubber (not metal, because it scratches the glass). I change the water and clean out old algae and vacuum up leftover foodstuffs. And scrub those walls.
But there's always a corner I miss, hidden behind an anemone I don't want to pester, or buried in sand that a crab just piled up in her everlasting building project. And whatever I want to look at always seems to hide right behind the messy corner.
I was watching a big, fat, shiny worm gobbling shrimp pellets, waiting for him to come within camera range (and he never did), and stopped to take a photo of a limpet eating, instead.
In the algae-infested corner, of course.
I usually delete these photos if I can't clean them up, but I kept this one, as is. The limpet is eating the algae; that's why she's in that corner.