Dog mites, tics or fleas?

[missycharlie]

My greyhounds came back from kennels following a week's holiday and on bathing them, I noticed that one of them had tiny black pinhead size beasties on his skin.  I've heard that tics and fleas are quite big and would be visible so what are these?  I've also read that as greyhounds have a low fat/body weight ratio that I have to be careful how I treat fleas, etc.  Some advice please.

[PurplePixie]

Fleas move very quickly through the hair if you disturb them, their poo is tiny black specks..could that be what you see?  If you scrape them off onto a damp tissue, it will leave a red stain (as it is made from blood)

Tics are about the size of fleas when they land on the dog, and about the size of a smartie when they are full of blood so it doesn't sound like a tic.