I would have to do some digging to find possible floating plants that are present in a specific habitat. Most angelfish live in shaded watercourses that do not have aquatic plants per say but do have overhanging or marginal vegetation. We use floating plants to replicate this.
Tropical (sometimes called Amazon) Frogbit (Limnobium laevigatum) is native to South America. Salvinia species are native to neotropical areas; this is a much smaller plant but it goes well with a larger floater like the Frogbit.
Water Sprite, Ceratopteris cornuta, is in my view "the" best floating plant, and it is now said to be found in the Americas though originally it was endemic to the old world, probably originating in Africa and spreading across southern Asia.
There is Pistia stratiotes, common name Water Lettuce. Unknown origin, but likely in the Tethys region which may be considered what today is East Africa, India, Indonesia back when these were connected. Pantropical today, this plant is found world-wide in tropical and subtropical regions.
The three above (not including Salvinia) are more substantial plants, and thus very useful as shade plants, sources of microscopic food, and water quality. Angelfish will love to browse slowly through the dangling roots of these floaters.
