24 hrs to be safe for most but total cure is some thing like 7days, but safe after 24 if you can touch it and it is not goowy or move under your finger then the out side layer is safe for saltwter. But I always wate 48 hrs to add water you never know with silicone you don't want to loss all your fish, in this hobby its always better to error on the safe side and go slow..

Bill