That is how they communicate. They make clicking sounds during feedign frenzy and skirmishes. If you notice the bifid spines found under each eye, you will see what I mean. Several of my loaches here do that when they peck each other. Tiger loaches have the loudest clicking sounds so far in my experience.
i noticed a lot of clicking when i gave their nightly feed of bloodworm. i noticed it more when they were eating. also scavenging and when they found something they liked.
yeah these guys are neat. especially when the whip out their little switchblades! so how do they actually "click"? do they make the noise with their jaws?