Many make the mistake of thinking that grimer and muk are capable of gaining nutrition from any kind of matter, whether organic or inorganic. While it is true that the species is willing to consume most materials, they have trouble digesting metals, rubber, and some kinds of plastic. In areas of Alola where refuse is partly disposed of by being fed to muks and grimers, dustbins are labelled according to what the species is able to digest.
While not a matter of dietary requirements, many serious competitive trainers feed their muks exclusively on fluids; the process of digesting solids can make them heavier and more cumbersome, which impacts on their performance in battle.
Some fire-type carnivores (such as pyroar, incineroar and houndooms) can grow ill from eating raw meat. As their typical hunting methods would usually see them ‘cook’ their prey, they never evolved to be able to stomach raw flesh in the way that other predators can. Other fire-type meat eaters - like arcanine and flareon - don’t have this problem.
Although many trainers have tried to convince their kadabras and alakazams to eat ice cream with their spoons, this is ill-advised in regards to dietary requirements. The abra line is lactose intolerant and eats very little. Their minimal diet is composed of smaller bugs, fruits, and lots of water.
Steelix are capable of digesting most rocks, but the high sodium and potassium content of alkalic minerals can make them briefly unwell.
It has been found that the different heads of species like doduo, dodrio and zweilous can have different allergens. This problem is most present in the doduo line; sometimes one head will react adversely to certain kinds of grain, causing the throat and tongue to swell. This can be difficult to deal with, as feeding one head separately from the others - which is necessary when one has allergies - often causes squabbling and aggressive behaviour.
While zoruas and zoroarks may be able to present as human, trainers must prevent them from eating human foods such as chocolate, onions and cheese, as much as they might want to.
Sometimes people take bags of fake gems to scatter and feed to the more adventurous sableye in the caves near Dewford. Clear glass gems aren’t harmful (though they aren’t particularly nutritious), but coloured gems can be toxic owing to the dyes used to create the pigments. Plastic gems are an absolute no-no, though most sableye are savvy enough to turn their nose up at them.
Some make the mistake of thinking that munna and musharna can sustain themselves on dreams alone. Rest assured, they also need a diet of fruit, veg and berries in order to thrive. Eggs are to be avoided.
Scrafties will frequently attempt to consume fizzy drinks and alcohol, even though both are toxic to them in large doses. It’s easy enough to keep trained ones away from the stuff, but if a wild scrafty pinches your cider, it’s probably best to just…let them be.