Has anyone put their Pond filter sponges through a washing machine?

Would it mess up or make the washing machine smell if I did it on a rinse cycle (19 mins on ours)

Get a bucket of pond water and wash them out in that. It's the same as if you own a fish tank. If you use a washing machine to do it you will wash out all the good bacteria on the filters needed to break down the waste.

Yes just rinse them in pond water. You shouldn't wash them intensely anyway, just lightly to get the main detritus off. As said, fresh water kills all the good bacteria that has built up over weeks and moths.

Definitely DON'T wash them in the washing machine as the washing detergent residue could kill your fish.

They will never be completely clean as they are designed to trap bacteria which is helpful to keeping the water clean. I wash mine under the cold tap in the garden.

No no no. The fresh water's killing off the good bacteria that's taken weeks to build up in your sponge so always just rinse it in a little pond or tank water!