Oh, okay. Can they be in sand? You could always buy play sand from Home Depot, 50 pounds costs around $5.
Do you just buy feeder guppies? If so I heard they aren't actually that good for them since pet stores neglect them even more.
He doesn't really like the sand..i've tried that and he wasn't too pleased..he however likes to rest on a flat rock i placed in thre centre of the tank . oh and i catch my gupppies from a dam...they are wild guppies ( mosquito fish) quite common here in trinidad and very nutritious for him :)