This page lists all of the Plort Statues currently available in the game. Each fountain has three statues of a single slime type. The Jetpack is necessary to be able to activate all of them.
If the favored food of these slimes have been obtained beforehand, Gordo Snares can be used to catch the Gordos of these slimes, saving the need to manually try and collect plorts in sequence of availability.
Tangle Plort Statues
Tangle Slimes can be found either by popping the Tangle Gordo, or restoring the Rock Fountain and feeding the Tangle Slimes that spawn from the oases in that area.
Rock Plort Statues
Rock Slimes can be found spawning in modest amounts along the path leading to the the area containing the Tangle Gordo.