Toz had lost his sword, so he had to conjure a new one that, while not as good as his previous one, would do for now. He used the sword to slash at the fish that got close to them while using whips of metal wire to attack those further away.
Nil used his understanding of the spell that he was in the middle of learning and sent sharp metal spikes raining down on the fish.
Lucy covered the trees and leaves, protecting them from the fish's attacks.
Mindle had to be careful of lighting the trees on fire even if Lucy was protecting them, so she attacked by targeting larger clumps of fish that were a little bit further away from the trees. She also used her control of heat to help Lucy keep the fish away from the trees by heating the air around them.