HOB skimmers. Can they do the same job as sump skimmers?

[Myka]

A UV sterilizer doesn't affect bioload. UV sterilizers generally will only kill algae in the water column, bt are advertised to control Ich. Most Uv sterilizers aren't even close to powerful enough to kill Ich.

Generally, you have to spend more money on an HOB skimmer to get good results than you would for an in-sump skimmer. An in-sump skimmer also comes with the cost of a return pump and plumbing too though. On a small tank, say less than 50 gallons, an HOB is a reasonable choice. Bigger tanks tend to function better with an in-sump skimmer.