... or, the aquatic ecosystem in the living room.
cayeux is continually amused and amazed (as am I) by the stability of the aquarium. We often go weeks between feedings, and yet the fish are all in fine health. I've got my black neon tetras, and a small green cory (catfish), and snails. There's hornwort growing, and Java moss, and several kinds of algae -- from the velvety, brown carpet algae growing on the sunken log to one that's new in the aquarium this year, a fibrous green algae that feels like cotton when you pull it apart.
The snails eat the algae, the fish eat the plants (and maybe sometimes the snails), their poop is broken down by bacteria and the nutrients are taken back up by the plants again. Nitrogen and phosphorus go 'round and 'round. Every once in a while I add some more in the form of fish food, and every once in a while I take some out by harvesting snails or algae or by changing some of the water.
Although, to be honest, I think the last time I changed any water must have been back in August ...