I kept a humu from about 2002 - 2008, and he was a fantastic fish to own. While he would eat smaller snails/ hermits, the large ones in big shells were safe, as he couldn't get a marble size shell in his mouth to crush.. He was very cool, and over time while I was out of town on work for 300+ days of the year, my mom came over to fed the fish daily (we live 3 blocks apart) - the fish became very friendly to her, actually allowing her to "pet" him daily. He suddenly died one day - tottaly unkown cause, no ich/disease - had a fat belly. was rather crushed by the loss...And he was very pretty, all those colors & lines..... these are the good times...
However, if you've ever owned a dog that chewed up the garden hoses, dug holes all over the backyard, tore up the flower garden, and buried anything YOU like - then that's alot like owning a humu.....that darn fish constantly moved the substrate from under rocks allowing them to fall over. He'd tip over corals & frags and bury them. He'd move smaller chunks of liverock around - bang them against the glass......He actually broke a submereged glass encased thermometer, shattering it. . . he'd take mouthfulls of substrate and spit them out over corals - even covering them sometimes - rocks too. He seemed to prefer a "dish" shapped bottom of the tank, as he kept the substate VERY low in the tank center, but kept it 6"+ deep at the ends/sides.......It was HIS tank, and I was just the feeder......you can beat a dog when it rips up the backyard, but you can only laugh at a mindless fish destroying "your" ideal habitat. I never saw evidence of mine eating coral - he just buired them, flipped them over and covered up with sand.
They can be a fantastic fish to own, but IME - they tend to do their own thing in the tank, owner be darned. I've NO plans to have another