I put in whatever the Jobo tank recommends, for example, last night I processed 6 sheets of 4x5 in the small 2500 series tank and they say to use 270mL. Comes out fine. I do reuse the bleach, though, since it can be reused and is the most expensive part. For 8x10 sheets in a 2500 tank, I use 125mL per sheet with great results.