What types of fish don't need a filter?

Technically, most fish can survive without pumps and air fulters in a large outdoor pond with a large surface area for ixygen to enter the water and plants to clean the water. However, if keeping them as pets you should always provide pumps and filters, ir they will live very short lives. Otherwise it would be similar to keeping a human in a dark crate with little oxygen and no waste disposal. do not belive that betta fish can live in these terrible conditions, as it is unfair to them