I've got 2 trochus and they do a good job but I've never seen them on the sand; always on either the rocks or glass.I have trochus snails / they can upright themselves and are great cleaners. And hermit crabs and Nasarius. I also have two tuxedo urchins that lawnmower through the tank eating algae! I did, however, buy very little ones since most of my corals are small frags. If they do get ahold of something, I just gently lift off with tweezers. Worth the effort!
As you saw in my post last week, I just got a Diamond Goby. My tank is also new - 5 months, but it had enough detritus and GHA clumps in sand to keep him fed. I also have a very healthy population of copepods, but that’s not his diet I believe. He actually devours everything I feed the fish! He jumps right in front of wrasse and grabs a mysis. And he has already cleaned my entire sandbed!
Maybe I could try to find a smaller urchin. With the diamond goby part of my concern is tank size as well. My display footprint is only 24"x16" and my sand bed is 1-1.5" deep.