Nutrient blocks are non-renewable (I think, at least without mods) and I want some food that gives the most food value while being renewable. It can be a plant or a fish, as I have the alien containment & both indoor and exterior growbeds.
If you are breeding Reginald's then create a Water Filtration Machine too, which will give you Large Filtered Water and Salt Deposits. You can use the salt to cure them which will prevent them from rotting, which combined with the water is good for long outings without a source of sustenance.