You find very little information about their diet and care because almost nothing is known.
It's thought that they're grazers of the organic film that grows on hard surfaces (but it's never been shown for sure). Because of that, most species only tend to do well in large, established tanks. L. multifora is the exception that sometimes does well in tanks as small as 55 gal.
They also have lots of shipping issues. They're fairly sensitive to salinity changes and without careful acclimation or a good dose of luck at every step of the way in the shipping chain, most are already doomed by the time they get to the store. It's best to buy these things locally and only after the LFS has held them for about 2 weeks. By that point, most shipping damage should become apparent as sores or dissolving/mushy limbs. Only buy an animal that is firm and plump. Once you get it home, be sure to drip acclimate it slowly too.