Removing fixer precipitate

I used accordion bottles to store my fixer. However I left one bottle of used fixer in the bottle for too long and the fixer starts to coat the silverish black substance on the inner surface of the bottle. May I ask if there are any reagents to clean off the residue? I read that using bottle brush is the way to go but this is an accordion bottle, thus a bottle brush may not be the best tool. Inputs appreciated.

First off, toss the accordion bottles, don't even bother with cleaning them. They allow oxygen to penetrate the bottle. Many folks use recycled soda or water bottles, of course glass is better. I got rid of all my "air-evac" bottles some time ago, dont regret it.

I use plastic milk bottles or plastic Distilled Water bottles for fixer. If I get the ppt on the walls of a bottle it costs me nothing to dispose of them. My time spent cleaning them is just a waste to me!

PE