Just for clarification, The Apple snails pictured are Pomacea Bridgesii AKA Mystery snails AKA Brigs. not to be confused with pomacea canaliculata Typically called apple snails AKA Cana's.
Both are members of the apple snail family, as are several other large snail species that are found in the hobby.
Cana's would go through that Hairgrass like a herd of sheep and leave nothing behind. Cana's do not come in the variety of colors that Brigs do. The Brigs are absolutely awesoe in a planted tank.
great pics of the snails aquabum.