a place to grow pods, even without caulerpa is beneficial. personally i'd suggest a separate sump/fuge system as I think that helped my system a ton. but even with the in tank, what i'd suggest is
first: go to your hardware store and get some fiberglass mesh (the type of stuff you use for window screens--just make sure it's the fiberglass kind, not metal) and wrap that around your pump. this will protect you (hopefully) from sucking any sand or caulerpa into the pump and thus damaging the pump.
second: get some caulerpa--perhaps a couple different kinds, and brace them with a rock or two--just wedge them between two rocks or put a little bit of a long strand under a rock. then you won't have caulerpa floating all around.
give this a try before you send it back, imo.
-leigh