Check on the grubs several times a week at least, and you can sift the substrate so it can be reused. I've read articles and seen pictures that show people washing the grubs
with water to clean the spiracles. A much different animal than the Dynastes and Lucanus a lot of us are used to.
When it's ready to pupate, it will lose weight, it will also stop eating and look for the substrate to do it in. I fed my grub a couple times a day, and never
found uneaten food. My care sheet never mentioned moistening the koi pellets, probably because of mold developing quicker. We get a care sheet from the breeder,
the seller, and expect it to contain the best information possible, the reality is that often it won't, or it only contains one person's experiences.
That's why you get conflicting information, you have to put all the information you can into a blender, and drink it down

.
Keep notes, and you can add them to the smoothie at some point.