Hi,
They are actually decent little skimmers. I honestly don't think I would put the CU-300 on anything over a 100gal tank though. They do work well for their price, but they are definitely overrated in my opinion.
For your 240 you might take a look at the ASM G4X, EuroReef CS250, AquaC EV400, or the Precision Marine Bullet 3.
Thanks,
Jeremy