Your tube looks to be a peanut worm, totally something you should leave in the tank. They are harmless, and great for consuming undesireables.
Clicking can also be a sign of a dreaded mantis shrimp, so keep that in mind. When I say "keep that in mind", don't just go assuming you have one and tear down your tank..probably wouldn't find it anyway, cuz they latch onto the rocks and really can dig in....I speak from personal experience...took out all my rocks, put them in a rubbermaid, combed through them with headlamp and forcepts, found nothing, put them back in...next night, heard the clicking again...
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Look for burrows near the base of your LR in the sand. Both types of shrimp use these burrows...or can use holes in the LR itself...though pistols I believe prefer the sand....I am not a pistol shrimp keeper
. There are plenty of traps available that you could put near the burrow (if found) in hopes you catch the culprit and get a 100% on the ID. It can take some time to catch these things though....they are some crafty critters.
I would suggest staying up at night a few times with a red light and the tank top open. Keep the lights off in the room like normal, turn off the pumps and powerheads, wait to hear clicking, toss in a piece of raw shrimp, wait a min, turn the red lamp on, and see if whatever made the noise is attacking the bait (cutting the pumps and powerheads off gives the bait more time to slowly release it's yummy goodness in the water without being sucked up, or deposited behind some rock where you can't see it, forcing said predator to dart from hiding to have a quick snack). That's how I got mine, had the net ready and by pure luck managed to get him out (mantis shrimp that is....they are quiiiiick). hope that helps, good luck.
On a side note, my Humu Trigger clicks like mad at night probably wants a snack to.....what a weirdo.
