Every other watering, with waterings every 3 day or so. Note that Cannabis loves molasses (use it as an addative).
when I had a drip emitter system with 4" rockwool, I would feed a 6 week old vegging plant every 3 hours for 5 min. during the light, and none during the dark. however now that I'm only using hydroton, I feed 24/7. When I had ebb/flow table for flowering, I would flood for 30 min. every 3 hours during the light, none during the dark.
Jeez, very complicated and misleading answers for a simple question. Don't feed a baby seedling at all until 2-3 weeks old. Thereafter, feed no more than once a week. Start at 1/4 the fert's recommended strength and slowly work up to about 1/2 strength. Less is more.