Abelone shells are awesome substrates to frag zoo's onto, get creative and glue various color into several spots on the shells, after a couple of months you'll then have a pretty amazing looking zoo garden....I can't remember where I read this, but it seems to really work better than using LR as the base for the frags, but it had to do with a research paper that studied using various bases for fragging and that the best responce was when a calcium type of substrate was used, ie any type of shell, old pieces of broken, dead coral. Even chunks of white marble, the type used in everday tiles.... I personally like to frag my zoo's onto abalone shells, as you can get them in sizes from about 1" up to 6", but I also use tonga branches to make really big frag gardens..