Simplify the following text for a Grade 9 native English-speaking person.
Original: Although whale sharks have very large mouths , they feed mainly , though not exclusively , on plankton , microscopic plants and animals , although the BBC program Planet Earth filmed a whale shark feeding on a school of small fish .
Simplified: Although whale sharks have very large mouths , they feed mainly , though not exclusively , on plankton , microscopic plants and animals . However , the BBC program Planet Earth filmed a whale shark feeding on a school of small fish .