Just my input on the subject,
I use fleece with all moms & kits. I have 2 males that will chew it, they don't get it.
I think the flies infest damp/wet areas, either from urine or a dripping water bottle.
In my years with chins I have never seen them, but we got a hamster that played tug tug with his water bottle that was continuously dripping on the wood floor of his cage.
I notice those teeny tiny flies someone mentioned here last spring on the door to the cage.
Moved the hamster to a plastic bottom cage and secured his water bottle.
flies gone.
I have also found some chins will chew any thing while others nothing. How much of what they chew do they eat we don't know, until it's too late.
I know folks that still have plastic shelves and that are not touched.
I just couldn't !!!!
I have always used pine shavings and /or unprinted news print now and then. I have never had a problem, but have been advised by my vet and others that some chins are showing up with respiratory problems they feel are due too the pine.
No matter how long I'm at it I'll never learn it all, nor remember it. I need the kind folks here to keep me up to date and to nudge me if I goof.
We're all here to Learn and share.
So Haru you think you'll be trying the sand
I wouldn't