feeding with lights off or on?

depends what hydro system u running

You are constantly feeding with hydro, so it doesn't matter!! Set your ppms and ph to where you want it, and then just keep it there! After 3 days from when I set it, I only check it every 2 or 3 days!

Depends on your system. But plants don't take up nutes when lights are out. But most of the time it's 3 times during lights on.

Only dwc and areo are non stop. Ebb and flow and ebb and grow, drip systems turn off. Nft can be both. But this also depends on you media you deside to use. Hydroton, RW, perlite, like more feedings then coco and coco mixes. Or atleast in my setup. I run a mix and water 2 times lights on. So to give a better answer please give more details on what you want to run.

im running ebb and flow

with hydroton

Then 3 times lights on. 1 hour after lights come on and 1 hour befor lights go off. And 1 mid way. The times change with 18/6 and 12/12 so you get the idea.

thank you very much!