An equivalent Octopus skimmer to the ones stated above would be more along the lines of the FDNW-400. Even there the ones I mentioned would out skim it.
Its not that the Octopus skimmers are bad, its just that their designs are not as efficient as the ones above so you need a much larger size octopus for the same size tank.
If you had a lightly or medium stocked tank I'd put a Reeflo 250 pro on it (instead of the octopus, same price range) as the Reeflo is a better design that the octopus, but less money that the ones I listed above.
However I'd look hard at an ATB large. Its not that much more than a reeflo, can be used internally, and will outskim a reeflo.
It really depends on your price range. At this level you can't buy a bad skimmer. You are merely buying ones that are more efficient.