Approaching the pools was not the easiest of tasks. They had to check the regular pools as they moved. If the group missed something, then they could have an enemy at their back. One that would easily beat them before they could even try to find a jade worm egg for Maria to raise.
'There are more crabs. They seem like they are eating any of the pale shrimp that try and come this way." Purple realized that the only reason the vibrant algae was able to be here was the fact that the crabs had managed to take root here. They did not eat algae or plants at all.
"I thought this would be the case. If we kill the crabs here we will ruin the pools that support the jade worms. They can't move fast enough to get to the vibrant green algae they need." Since Maria understood this, she didn't make a move to battle the crabs that could sense them as predators outside their pools.