18??? LOL You have your work cut out for you! I refuse to brood more than 10 at once! Hopefully your brooder is very large, and outdoors.
I saw someone that used a baby pool with straw, that may make a larger number more manageable. I've found that the mess is helped if you rig a container for the water to set in. I only have 6 ducklings brooding right now, and a paint roller tray gives them access to it and contains the mess fairly well.
You want the food well away from the water. The closer it is, the bigger the mess and worse the smell because of how fast the food gets wet.
I altered my brooder (that's wood) for the next batch of hatchlings to have a vinyl floor and also secured plastic shelf liner to the sides and sealed it all up with liquid nails. My 3 week old group of 6 have graduated to an XXL dog crate with towels draped over the sides to catch the slung around water/food mixture and hold in a bit of heat.
Chickens kick stuff around and fill their water with bedding and make their own sort of mess. But ducks... Ducklings do this thing where they "filter" the water with their beaks, a super fast vibration type of thing, that of course sends it everywhere. They eat 3 bites of food, then swish it in water. So the mixing of the food and water with the motion of the beak, sends the stuff everywhere. That wet mixture can either fall into a container, or right onto the brooder floor and soak through the bedding.
And they poo a lot, large, wet, poo. Chickens make nice dry little bits of poo, usually. Ducklings... think of a 4 month old pullet who drinks a LOT of water.
Ducks are designed to live in wide open spaces. Not little boxes. Makes for a lot of work for the human who insists on brooding them.
Usually I hatch chickens in November to have early eggs the next year. I will not be doing that with ducks unless I move much farther south.
