I have 2 ducklings that are about a week old, and their tank already smells terrible. They are in a large black stock tank with sand for bedding. I'm assuming the smells is due to the water they manage to get everywhere, as i had 6 chicks in the same tank for a month and never got one whiff of a bad smell. So, what can i do to eliminate the smell, and what age can the ducklings go outside (with a heat lamp, of course)?