refugium

noun2

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. — 2016
2. •
   A separate section of a fishtank that shares the same water supply, used for denitrification, plankton production, etc.