how much food for vlamingi?

I have recently added a 3 inch vlamingi tang to my aquarium. I have about 75 pound LR for grazing but I dont base feeding off of this. I only have the tang and a banggai cardinal, which the cardinal doesnt touch algae - so the only algae eater is the vlamingi.
How much nori should i feed a day? I have those sheets that are about 10" x 10'', and wonder if there is a ball park amount of how much he should eat daily.
I have also tried fresh romaine, but he is no go with that - for now...

 

I put a 1/4 of a sheet in every other day for my vlamingi and yellow. They eat it up and are fat. They also eat on the other food as well.


EDIT: I will need to put more in as they grow.

 

I would put in a piece about the size of a credit card in daily.
You can try raw broccoli too. Does wonders for their immune systems