So the fish store that sold them to you - solely to cycle your tank - will not take them back when you're done with them?!! Like you said... who wants eight damsels (let alone 2) in a 55g tank. I'd even go out on a limb and say 8 damsels in a 55g is way too many, even if you wanted damsels!!
That's really a bad deal if the LFS
won't take them back - even when you're done with your cycle. (And if they will take them back when your cycle is complete, I'd be magically "done" with my cycle and return them!)
As Pat mentioned, 2 damsels will cycle that tank. In the mean time, I'd find a new LFS
. Seems like if a store if going to tell folks to use their damsels to cycle a tank, they should at least take them back for *some* amount of credit when you're done.
Just noticed you mentioned 3 lbs of live rock. Is that a typo? Only 3 pounds? If that's correct, what other biological filtration do you have going with the tank. Any hang-on back filters, bioballs, etc?