Now I know other places on this site will say that the Red Sea Prizm skimmer is both good and bad, but I think it works amazingly well. SeaClone is a joke and disaster, and my friend has a coralife that refuses to work right no matter how well he cleans it and then lets it run. Every other week (without any additives or spraying!!!!) he has a little overflow. His tank is in a basement with tile so it's not a huge deal, but I have had the prizm for a while now, and especially for the price, I think it can't be beat unless you get an in-sump system, but since you asked about HOB, that's what I'll talk about!