bulk head question

[Deranged-Jester]

howdy all,
i know its a dumb one. but which side does the rubber gasket go on the bulkhead? inside the aquarium or out?

 

[silverwolf72]

the opposite side of the not. nut on outside= washer on inside

 

[papagimp]

inside.

If you had stuck it on the outside, then it wouldn't have seemed like a stupid question later on during an H20 leak.