I will have to disagree a HOB
is most certainly a technically a "fuge". The Aquaclear refuge set up does just what any refugium is meant to do. It protects organisms (wheter, isopods, algaes, etc..) from predation from tank mates. Nothing more nothing less.
Many do more than chuck live rock rubble in it, mangroves, macros, etc... Plastic egg shell crating is often used to help keep the flow from blasting out macros. The DIY section at www.nano-reef.com
is a good place to search.