If you are considering breeding these, go slam your hand in a car door a few times. It will be much less painful. Literally one veggie cake per percent of growth....and it grows slow.. Digests roughly one point of food per second, so feed a cake about one for every 7 mins (during event boost) and it will gain one percent of growth.
They worth the veggie cake. It gives 100 paste and organic polymer. Just level up their food so they won't be hungry fast.
I have 2 bee hives and 7 tree sap taps (important to make veggie cakes). I can produce more cakes than what my 2 achatina can consume at a time. Now, I never run out of paste and have a lot of veggie cakes (I needed separate refrigerator just for my cakes)