Silver fish, Little Buggers
 

We've got a light tube skylight in our house, and whats annoying is that silverfish get in and are visible in the bottom diffuser dome.

Anyone have any experience dealing with this problem.

Sounds like the whole window wasn't properly sealed or installed. Insects shouldn't be able to get in between window panes, and that's obviously what's happening.

Personally, I would have a new one installed, either by the contractor that did it or on your own. If that's not an option, you need to figure out where they're getting in. If it is a gap in between the panes, you'll most likely need to replace the whole unit. If not, you can try sealing the hole with caulk or putty and see what happens.