An outdoor fish-pond is a lovely idea. Beautiful koi swimming around, water flowing in a fountain, and an attractive little foot-bridge along the path leading to the door.
Some things are better in concept than in actuality. The paper version of this beautiful scenario falls apart when exposed to the daily dampness of the water and the growth of algae in the pond. In the rainy season the pond becomes very, very full. The electrical system reveals flaws in the planning and wiring of the fountain pump when it gets flooded and shorts out the circuit in the house, and the mosquitoes grow more readily in still water than in moving water. Then comes the day when you need to move something into or out of your house. That picturesque little stepped bridge is not so pleasant to cross when you are moving a piano or carrying several bags of groceries. Only one person can cross at a time, making moving large objects even more challenging.
An outdoor fish-pond is a lovely idea, but I prefer living with tile or cement. How mundane of me.