More on Fluoride Trays

So I've gone back and gotten some new fluoride trays built. The sets I've had in the past have consistently picked up a nasty coating, or were actually impregnated with residue from the Gel Cam and perhaps food debris. In other words, they got absolutely nasty looking, and nothing I did could get this stuff off. It became so bad I had to not look at them while inserting. Sorry if that image makes you queasy.

I don't like Gel Cam. It stains teeth with a brown film, and it turns to a silly-putty like glue in the sink drain. Over the years, I've had to dismantle the drains of my bathroom sinks on a number of occasions to dig this residue out.

I've got my new trays. They look so nice and clean. I'm soaking them in denture cleaner each night after use, but I have no idea if this will prevent the nasties from coming back. Any suggestions?