phytoplankton culture help

[donkey77]

ok i got a setup from a member on here, its the whole setup, 3 gallon set up my ? is do i fill it up all the way with saltwater leaving enough to put 500ml of phytoplankton in and the f2 fert, and when i split do i leave half in and put new salt water in and the fert to keep the culture going, and do i have to put the split cultures in the fridge, sorry guys a lot of ?? i just don't wanna mess things up
thanks