I gave Nim the medical rat last Thursday. He tried to take the rat sideways for the first time, and eventually swallowed it backwards. I think he's ready to size up to weaned rats, but I used a pup for this because I wanted to make sure he'd eat it. I fed him a second, un-nexgarded pup rat which he ate normally. I wonder whether taking it sideways then backwards was somehow caused by the taste or smell of nexgard around the rat's mouth, or if it was just bad luck. He started nearer the front and took a long time to work his way around to try the back.
I saw no live mites while cleaning the enclosure today. I normally would see 0-3 mites on Nim himself, and while soaking him today I have so far seen none. Hopefully the number of dead mites will now begin to decline as well. Nim seems to be behaving normally today, so at least for now the nexgard doesn't seem to be causing him acute harm.
I am still treating the enclosure with PAM and have ordered two more cans because the first is close to running low.