Aptly forms an aquarium exhibit (5)

I believe the answer is:

platy

I'm a little stuck... Click here to teach me more about this clue!

'an aquarium exhibit' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'aptly forms' is the wordplay.
'forms' indicates anagramming the letters.
'aptly' anagrammed gives 'PLATY'.

Can you help me to learn more?

(Another definition for platy that I've seen is " Fish".)

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.