noun, plural o·cea·nar·i·ums, o·cea·nar·i·a [oh-shuh-nair-ee-uh]. a large saltwater aquarium for the display and observation of fish and other marine life.

What does the word oceanarium mean?

: a large marine aquarium.

Is fishtank one word or two?

a glass-sided tank for keeping, displaying, or observing live fish or other aquatic animals.