Sheryl,
I believe captive bred have been known to spawn at 1 1/2 years. There is no set time for clowns to start spawning. They can be coaxed in ways, but there is no sure fire way to know when they will spawn... Mine took a year to start after showing cleaning behavior. It's all up to them.. What type of clowns? Maroons do this just to make their caretakers unhappy it seems..
If both clowns work to clean a spot, it's just a matter of time.
Have you read Wilkerson's book?
Must read if you wanna raise some clowns.
Kevin