They are excellent escape artists, so be sure to have the tank locked down tight on top. Filter overflows, sumps, floor, you name it. I hated when I worked at a LFS (well, not local to here ) and we got them in... they always found their way into the sumps of our systems.
Edit: but they are nice looking! Aren't they the ones were the male and female are different colors (like blue for one, and yellow for the other?).