like in the wild, sometimes a gecko may consume substrates. To reduce the chances of having impaction, use a substrate that doesn't contain many large chunks. To completely eliminate the problem, paper towels may be used for some arboreal species, as well as some ground species. Paper towels would need to be changes weekly to maintain cleanliness.
Monito gecko's eat insects and spiders
Substrate feeders eat the organic matter that accumulates at the bottom...and that includes faeces.
sometimes
A good substrate is one to retain moisture for humidity purposes. Peat moss/coco-husk and eco earth mix works great for holding moisture.
nothing
crickets ;)
Consult a veterinarian.
yes they do
they eat insects.
MOUSE
Yes. As long as you don't make it too tight on your gecko. Don't leave it on him/she for too long. (For more information, look up How do you make a leopard gecko leash)
force feed it