New Baby leo sick

Question

Leo  

Sick   I just recently bought a baby leopard gecko from the pet store last Tuesday. For a little info on his cage and setup: He is in a 10gal tank with an under tank heater and dome lights (red and white). The temp is usually 90 on the hot side and 75 on the cool side.He has two hides one on each side. A bowl of mealworms always inside the cage and a bowl with calcium and water. My leopard gecko is really thin and hasn't eaten a thing since I have had him. I will add a picture of him so you can see. Also I have notice some green poop im guessing under his tail, it is also red and looks irritated. I really don't want to just take him back for a different one at the pet store.

I have added two pictures. One taken a few days ago and one taken 5min ago. the one just recently shows under his tail. He was laying in that position when I looked at him on his own.

HELPPPPP"

Answer
Bad news:  Your leopard gecko is so emaciated, he's nearly too far gone to save.  Your options are to take him back--he will most certainly die, as the pet store is unlikely to provide vet care--or to immediately take him to an experienced reptile veterinarian--or euthanize him.  He may not make it, even with treatment.  The store sold you an animal that was already so sick, there was little hope.  A leopard gecko won't get into that condition in just a week.  Based on what you described, he could have internal parasites, such as coccidia, or worse.

If you decide to get a different gecko later, disinfect everything with a 10% bleach solution left on for 5 minutes, and throw away anything you cannot disinfect.  (Rinse well until no bleach odor remains).  Do not use an undertank heat pad without a controlling device such as a rheostat or thermostat.  They will overheat and burn the animal.
I can't tell whether you're using a sand-colored cage carpet (which is fine), or sand.  Sand poses a danger to leopard geckos, as some of them will, for unknown reasons, eat it.  It blocks their intestinal tract.
Use a thermometer with a remote probe.  You can buy indoor/outdoor thermometers with remote probes for $12 at Walmart.  The stick-on dial types sold in pet stores are about as useful as drawing one on a piece of paper, and can be inaccurate up to 30 degrees!  (They should not be legal to sell, but they are still being sold).

If you decide to try to save him, be prepared for weeks of treatment (if he makes it).  The vet will need a fresh (not dried) fecal sample to diagnose parasites.