I am curious from which material your sink was made?
Your post brought me back to my years working with a professional b/w printer from my early twenties. Cleaning the trays and the sink at the end of the day was part of my job. I combined this with actively washing the print we had made. We had two large pvc sinks standing against two walls and they followed the corner of the room. Each sink was large enough to have three 50X60cm (20X24) trays, or four trays for any of the smaller sizes.
The developing tray was cleaned for an hour with old fix, just letting it sit in there. The other trays were simply rinsed with quite warm water. The developing tray, once the old fix went back into the jerry-can, was rinsed with very warm water too. By the time that was done all the trays moved to the second sink where the prints were being washed. The trays we stood up against the back of the sink, to let the water out. Then the first sink was cleaned, first with warm water and then I used a large soft brush in combination with the water, to make sure everything was clean. That was from 1980 and on. I have seen these sinks go past the year 2000 and they never got dirty or damaged. The first sink for my own darkroom I made from wood and a two components paint, it never got dirty. I replaced that one with my current pvc sink more than 10 years ago. Same story. All the sinks I talk about were and are used professionally, meaning pretty much on a daily basis.
Sorry I was so long, obviously my question is why put anything in there?