I dont think you need any of that - think about it
for the food to get to the tank from the fridge the tubes have to leave the fridge so why at any point does the doser have to be in the fridge, instead have the containers in the fridge and the doser on the outside sucking the food out, through the doser and onto the tank, this is no different than me having my doser feed my system with the balling method from chambers under the tank.