refugium

noun

1. Any local environment that has escaped regional ecological change and therefore provides a habitat for endangered species.

   “Beetles fly, many ants send forth massive swarms of reproductive alate females and males, arachnids and insect predators emerge from their hidden refugia, and termite swarm.”

2. A separate section of a fishtank that shares the same water supply, used for denitrification, plankton production, etc.