A canopy is the whole unit that sits on the top of the main tank, which includes the lighting, plexi cover that protects the lights from water splatter, etc. Some have doors on the front that swing open, and others have a front that raises up to open the tank for maintenance, feeding, etc.
I will be making the canopy so that it is also escape proof, so the fire eels I get won't be able to get out. Will be closed on all sides, with the canister filter intake and outputs going through holes drilled specifically for them.