Timmyjoe
Veteran
I usually mix up 20oz of fixer and put 15 rolls through it max. If I notice it getting dirty I dump it. So anywhere from 5-15.
I was thinking the same thing as far as fixer. The build up you have on your plastic reels looks like the buildup I get in the plastic containers I use for fixer. Basically a build up of dirty silver. I know I stretch my fixer too long, and as a result it can't hold the amount of silver I'm asking it to, so it deposits it on the plastic surfaces.
Just a thought.