Anyone figured out how to prevent light leakage from a HOB refugium?

[TerraFerma]

I'm in the market to run a HOB refugium (pre fab or converted HOB filter). But I can't figure out how to not light up the tank at night. Anyone figured out an at least partially effective solution to this?

 

[Julian A McRae]

I have an aquafuge and used black tape to black out the hob and it prevents any light bleed, also made a window in it to see whats going on in it if i want