I have some experience mainly in aquarium but some in natural ponds. Duck weed probably the easiest can be raised in a large bowl and provides great cover for baby fish and insect larva such as mosquitoes. Water lilies depending on the type can take up a lot of space. Also if you have a filter system in place duck weed can clog up this(along with a few other water crops)
Read that if you harvest, cake and dry duck weed that it is excellent for chicken and poultry. Kind of wondering if it is just a throw it in the pond and it will grow or if it has special requirements.