I have the old prism skimmer on my 30
gal. tank and am not really happy with it, I am using Berlin's turbo skimmer on my 75
gal. reef and I am very happy with this skimmer. I have tried a couple of others but they were'nt worth the money (Big Mombassa).
im sure there are other good ones out there, someone will post there likes and dislikes and you can then study the different types and make your decision.
Good luck