I used both Reef Octopus classic 90 and Reef Octopus HOB-2000. Both worked like a charm for my smaller tanks without a sump. But even after I upgraded to a tank with sump, I kept the HOB-2000 running in the sump for over a year.
You will have to have ATO though. If water level is not consistent, you will have lots of headache tuning any skimmer in.
You will have to have ATO though. If water level is not consistent, you will have lots of headache tuning any skimmer in.