This project started with a very ordinary problem: my Xiaomi aquarium broke out in green algae. The glass looked like someone had rolled out a green carpet across it. The snails were behaving oddly, too — the apple snail kept climbing above the waterline, and the nerite parked itself on the glass and stayed there for the better part of a week. The three zebra danios, meanwhile, were perfectly happy, cruising around like nothing had changed.