How big should my spawning pond be?

[Joshaeus]

Hi all! I am planning to keep the killifish Aphanius mento (hardy from 36 to about 95 degrees) in a water garden next year, and I wanted to spawn them in the water garden and raise the fry. However...how big of a container should I use for the task? Here's a few facts to help you help me;
- Aphanius sp. are ravenous egg and fry eaters, but are only about 2 inches long
- I am thinking about an 18 gallon round storage tote, a 40 gallon tuff stuff trough, or an 110 gallon tuff stuff trough
- It will be heavily planted with hornwort, water lettuce, and a water lily

So...which container should I go with? Thanks