When I first started the hobby I used to buy from anywhere (inc garden centres) for my live rock), it was about 6 months later and ready to get the whole cycle going I started losing a few small fish and was convinced they were jumping and being eaten by our dog! It wasn’t until I bought some yellow tailed damsels and saw them reversing to certain areas of the sand and disturbing the surface, that I realised something was going on and I started to research their behaviour, it turned out they do this to expose predators and warn off others especially when it comes to ‘Bobbit worms’. With a sand sieve I scooped up the area they were disturbing to discover a 7-8” Bobbit that was very aggressive to say the least and I struggled at first to keep it in the sieve, since this I now throughly dip and quarantine anything that goes near my tank and it certainly proved the ‘new starter’ theory and my lack of experience in the hobby to never take anything for granted.I wasn't sure what it was but it was just over a sand hill. I could see like 2 cm long finger leather looking strings that were extending and then curling back down. I studied it and tried to take a picture but couldn't. I couldn't see the pit of it because of the sand. I should have turned off my return and looked from above.. I tested if it would respond to shadows. It did not. I decided to try and scoop it out with a little measuring scoop as I was uncertain it was a worm. When I went for it; it was too close to the rock and it receded back down into the sand and probably that rock. I had only a bit of sand.
I have 55 lbs of gulf live rock. I am about to search up some worms..