well i think this glowing thing could be a sort of jellyfish and the ooze is bakteria, like a sponge, but liquid, and the jellyfish forces the cells of the ooze to do what he likes this pheromones and "trick or treat"-style. So the fish can travel on land trough dark caves always knowing where it goes for the light. This way there are no enemies and the symbiosis with the ooze is a great success because now the jellyfish can hunt little land animals that dont count with him here. Easy hunting. The bakteria get the rest of the prey, they share it. i think they are about 2 feet tall and fast like a running child.
The eggs of the JF are save there too. They can grow in safty till they can controll thier own ooze.