I did this with my turtles years ago. They ate whatever went in the tank so I was cultivating frogbit of salvinia in my 5g fish tank at the time. As it grew to cover the surface I would remove it and feed the turtles.
As for ferts, SeaChem makes good liquid ferts but there are members here who make their own for NPT's. They make dry Macro nutrient mixes. I never understood it but maybe they'll find their way here! Good luck!