Diatomaceous earth is made up of the skeletal remains of diatoms which are microscopic water dwelling creatures. It is really only effective for soft bodied insects such as grubs, slugs, worms and the like. As the insect comes in contact with the earth it's skin is pierced by the sharp edges of the diatom which causes it to die from dehydration as all its bug juice innards leak out of the cuts.
I can see where it could be a problem if a cham ingested it. You may be able to layer it into the soil and cover it with more soil or rocks.