I never once thought about this and won’t in the future either. Go ahead and rinse if you like it. These have been used for many purposes over the years so mine were probably cleaned at some point in the past before I used for this.
with two tidy cats buckets I filled them every 3-4 weeks with 6 laying hens. if you are ok refilling that frequently,
Maybe every 3weekends or a little bit more often, two will be great.
Have you removed all other food sources? Chuck some scrambled eggs in the flat part at the entrance and some more down in the bottom. Sit back and observe. Bet they can get it.
At 7 weeks I am still using smaller elbows. Here are
My 3 sizes - the one with the measuring tape is for adults, slightly smaller tidy cats for 3-10 weeks or so, and the coffee can for 2-3 weeks.