I'd love to see photos! I just can't imagine chips under ducks that aren't slimy and gross. Perhaps it's your excellent drainage underneath. I do only have a dirt floor under mine that's clay soil with crappy drainage, which I'm sure isn't helping a bit.
I also wouldn't recommend deep litter for ducks. It works great for my chickens, but I tried deep wood chips in my duck coop and . Even if you don't keep water in the coop, ducks poo water..or rather, poo slime. Within one day, every chip of that litter was a soaked, slimy, slippery disgusting...
How do you all manage your floors, poop-wise? We've had our 11 in the coop (dirt floor) for not even two weeks and the ground is already a mucky, slimy, pooey mess. I've tried shavings which just get mucky too and shoved into the ground, and taking a pick/shovel to the whole thing to stir the...
I'll answer as best I can although I'm fairly new to duck ownership myself. (By a few months.) I've never heard personally a specific space amount for ducks, but I've used the same allowance as for LF chickens in my coop/run design.. 4 sq ft per bird in coop, 10 sq ft per bird in run. And nope...