I use an old school venturi skimmer on my tank and it works great. I bought it used at an LFS for $40. Put an ad on Craiglist or post a note at your LFS looking for a used skimmer. You can probably find a simpler design for much less money.
Check Aquaticeco.com They specialize in aquaculture equipment, so finding gear for a large aquarium can be cheaper through them.