The minimum amount of developer required is different for each developer.
You need to check the data sheet from the manufacturer for the product you're using
Thank you Leigh, I actually checked the fact sheet from Kodak and along their capacity table and the dilution I use it is around 750ml, I simply could not fit more than 800ml in the tray and still be able to safely shuffle the stack.
There are always two people in every picture: the photographer and the viewer.
~ Ansel Adams