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Yes, clump immediately, but mine sit under the ecoglow for 2 days before they come investigate. The sand is perfectly appropriate for the grass- really, they pick at the dirt, more than the grass....and scratch and scratch and scratch at it!
 
I like Exact and Kaytee, but I think they are essentially similar, as baby parrots' systems are fairly particular.
 
I only sand VERY dark eggs, such as Marans, Penedescencas, Empordanesas, etc. Marans eggs have a thick color coat and it seems less permeable than the normal shell, but even moreso, less permeable after shipping. Local or home eggs don't have issues.
 
The shell thickness isn't different, and the Marans must be allowed free-choice oyster shell like any other, as thin shells are more likely to break internally, leading to yolk peritonitis and death 
Don't let anyone tell you not to give oyster shell, folks!
 
I'm off to the farm- running late and I'm SURE the biddies are going to be cursing me...One girl WAILS at the top of her lungs until she's let out...sounds like you're peeling her toes. Such a noise!!