Corals and filter feeding invertebrates all take in food particles from the water, but each species takes in items of different sizes. Because of this, aquarium keepers must feed planktonic supplements that cover a broad range of particle sizes, ranging from 1 to 500 µm (micrometers) at the very least. This broad range will feed the corals and invertebrates even with the tiniest mouths, while also targeting those that need larger food items. Most of plankton supplements have particles that are at one end of the size range or the other, but you’ll probably never see all sizes covered with just one product. Instead, you have to use multiple supplements to meet the nutritional needs of filter feeding corals.