Sure. I keep Rhonda Kay in 24" water containers each year. They'll likely stay small if you keep their container under water small. They'll still spread out across the pond if they get happy enough, though. There are many, many other flowering pond plants, from water poppies to water hawthorne if you're looking for alternatives.
The type of fish will make a difference, though. Some fish will uproot everything, and others will eat many plants. Small tropicals might be all right.
