Google the skimmer model, after the name and model, add "review" without the quotes. you should hit lots of pages that should help you.
But if you see the description it says it Requires a 650-780 GPH pump to operate. That seems to me the pump is extra, bringing up the price.
i just bought that skimmer, and a oceanrunner 2700 NW, im gonna do the recirculating mod on that thing and see how it works, supposely it will be the same as a RC6-2
I think there was a pretty big thread on RC about that skimmer. From what Ive read, its a pretty good skimmer (the one with the needlewheel), however its very sensitive. I think you can get an asm skimmer for your 75 which will be great, or even the aquac ev 120, thas the one that Im using and it kicks ass