how much should they eat?

Question
I recently adopted 3 rats from a rescue, bringing me to 5 total. I feed them lab blocks daily, daily fresh fruits/veggies and 2-3 times a week a scoop of a homemade mix (oats, dried whole wheat pasta, total cereal, puffed rice).
I'm trying to figure out how much I should be giving them, as they seem to be plowing through food much more quickly, but then there ARE 3 more mouths. Is it OK to just free feed unless I see a weight problem starting?
Thanks!  

Answer
Absolutely free feed...keep the bowl full, because you never know if one isnt getting enough should another be hoarding the food. Your rats should not get overweight if they are eating the right kinds of foods. They usually know when to not overeat by instinct. A rat in the wild cannot move as quickly with an overly full tummy so they know to eat when satisfied, not when stuffed to the max.  Again, as long as the foods they get are not full of fats, proteins and all the unwanted stuff, and of course get their share of exercise out of the cage, they wont get chubby.

Just a side note...they are new to your home and also to each other, so they may seem to eat more right now because they may not have been fed well prior to coming to your home since they are rescues. They should slow down once they see food will be available at all times.