answer this question....
whats the total gallonage of the system?
what livestock are you putting in the tank?
how many fish are you putting in the system?
how often do you want to do water change?
whats your budget?
internal or external?
if you have the money to buy bubble king sm 250 or ATB 10.5, you can't go wrong if you like internal skimmer.
if you want cheap but great old school external skimmer like reeflo orca are bargains same as euroreef RC series since they are still manufacture under different name. Reeflo as MRC and euroreef as reef dynamics same design not as SEXY as new cone skimmer in the market now but they work a lot better IMO>
i have atb 12.5 deluxe in my main tank works great, energy efficient, very quiet and SEXY but i think my reeflo orca works a little better since its rated for over 1000 gallons and its external which means i can control the flow thru the skimmer.