I have an old goldfish bowl which used to be a 'fish hospital' but now just has some plants and rocks in it as an alternative houseplant, essentially. It has been like this for over a year without any algae or other 'problems'.
Today though I notice specks buzzing about inside the bowl. Closer inspection showed they weren't bubble or crud diffusing about. Even closer inspection showed that the bowl is now home to Daphnia, a freshwater crustacean better known as 'water fleas' for the darting motion they make as they move through the water.
I have no idea where these came from but I might see if I can keep the colony alive.
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