Is there is a certain amount of chemicals (Developer & Fixer) that you should fill the trays with based upon how many prints you expect to process? When i print i use Ilford Mg developer 1+9 that gives me 20 ounces of developer (2oz developer & 18oz water). I also use Kodafix at 2.5oz Kodafix & 17.50z water. When i make an 8x10 print i usually go through about 6 sheets before i like the print. i know the developer is fine because i have not seen any difference of development from the 1st to the 6th print but i dont know about the fixer. Is there a certain amount is should use based upon how many print i expect to do? Thanks!