Sea Urchins

As you may or may not know, I have a purple hairy pincushion urchin cruising around my tank. It likes to pick up my snails, frags, and anything else it can find and wear them as hats. My question is, how aware are these guys of their environment? I know they don't have eyes, nor do they have anything I can really equate to a nose or ears, but my urchin always rushes (as much as a urchin rushes anywhere) to check out something new in the tank. Right now he's sitting on top of my new Midas blenny's chosen hideout (no worries, there are multiple exits, so he isn't trapped). The urchin also always seems to know when I tie algae sheets to a rock, and he rushes over to be the first in line at the buffet, so to speak. It doesn't matter where I tie the algae. The urchin just cruises on over to it. And if I remove a frag hat and replace it where it was, he just goes right back over and picks it back up. Usually I have to place the frag somewhere else in the tank until he's away from its original home; then I put it back where it's supposed to be.

Is all that normal, and if so, how do these guys figure out what's going on?

I dont know how aware they are but it is normal for them to behave that way. Mine does the same thing. I have learned to NEVER put a frag without securing it somehow. I will wake up in the morning and never find it again.

You can use super glue gel, if I am not sure I want it to be a permanent place for the frag I will just use a little bit just enough for it to be hard for him to pick up but not hard for me to break loose if I decide to move it.

And you can forget trying to have any macroalgae, mine eats ALL mine even my cheato. SIGH