I have been calling around looking for sand and one of the businesses that I called said that they sold "washed sand". What is washed sand? Is it ok to put in my peafowl's aviary? Does anyone have washed sand in with their peacocks? They quoted a price of $6.00 a yard for the washed sand. The lady on the phone said that washed sand goes through some type of process where it gets the "clumps" out? What clumps?