if i have a foam rock wall and some small bits of rock work in a 15gal can i have a pair of percs in there..i dont plan on getting a nem b/c im pretty sure no nem would stay small enough but maby like a frogspawn os somthing..i have a pair on the way and all i have at the moment is a 15gal that is cycled so i just wanted to know if i need to have my LFS hold them for a couple of weeks or if they would be ok