There are many opinions on this topic and there are several good brands including Deltec. Personally, I have used Reef Octopus skimmers for over 10 years and am currently using 3 different Reef Octopus skimmers on different systems. Additionally, in an informal R2R poll Reef Octopus was selected as the best skimmer brand:
Let's talk protein skimmers today and put it to a vote! 1. What brand skimmer are you running on your saltwater reef aquarium? 2. Are you happy with your current skimmer? 3. If you could choose any skimmer what brand would you choose? VOTE on your favorite brand and if I forgot a good one...
Take a look at the tunze 9410 dc.
I have been running one in my 120G for 15 months.
Easiest skimmer to clean, you dont even have to turn it off.
Anti overflow.
I have not adjusted it since I turned it on 15 months ago.
I have taken it out twice to clean. Put it back in, turned it on, and it was right back to doing its job with no adjustment.
No need to turn it off when feeding or working in the tank.
Very underrated skimmer.