I use stopcock grease (spare me the comments, I've heard 'em all !). That is just a pure silicone grease made by Dow Corning for use in labs. It's inert and won't hurt anything.

While you can often get away without anything, it is better to use silicone grease for a better seal without binding, pinching and with a LOT less pressure.

HEHEHEHE

Lifeguard
 

Anyone know where I might be able to obtain this Lifeguard silicon Lubricant?

I get mine from J&L but you can get silicone lube at any plumbing supplies store or dive shop ( probably not many of those in Calgary tho)

vaseline??

I would not use vaseline
It is a petroleum product

I have used vaseline on o-rings. Bulkhead gaskets go on dry.

Vasaline is great for dry skin but I'm not sure if I'd use it in my aquarium.