I def agree with the heat, you need to raise the temps but i think that's been established by everyone else lol. I have a few other thoughts that may or may not help you.
1. Security. Some dragons feel threatened for various reasons no matter what you do or don't do. I would try putting up some paper around the sides of the glass of your 10 gallon to give your dragon some security and privacy. This can really help some dragons who otherwise are to worried about what's going on or who's watching to eat.
2. Light. If the cage is too dark the dragon may not be stimulated enough to eat. Make sure the cage is nice and bright so your dragon realizes it's daytime and he should be out and about hunting for food.
3. Crix Size. Too large of crix are extremely dangerous, and again I think that's already been established. However, I wanted to point out that regardless of that (even though that is extremely important) your dragon may not be eating bc he realizes it's too big for him. He may be eating the one and even though yes he's digesting it, he may realize how difficult it was for him and "upset" him internally therefor he is unlikely or unable to eat again until the too large of an item has passed.
3a. Pinhead crix are way to small. Start with 1/4" and go from there.
4. Genetics. It's possible this dragon will never grow right and/or gain weight if he was the runt or some other genetic problem. However, with eating the small amount that he does I doubt that this is the problem, but it is something to think about.
5. Old Standards. This is in no way meant as a slam to your friend or any other person out there, but it's a well known fact that most standards or "views" on how reptiles should be raised that are 10 or 20 years old are wrong. Sometimes people get stuck doing certain things bc that's just the way they do things whether it's right or wrong. If you go back and read reptile books that are 10 years old you would be amazed at what most of them say... now a days we have learned and improved upon the husbandry of reptiles which is why they are living longer and thriving more. So just because someone has been doing something forever really doesn't mean alot. It's what you learn and how you apply it that matters. I could do something for 40 years and still be terrible at it.
Again, that's not a slam on your friend. I'm no expert by any means but I'm smart enough to realize that certain basic things are the way dragons need to be taken care of... and that's just my 2 cents. Sorry for the long email I really hope your dragon does better with the high temps and smaller prey.
brandon
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Dragons by Nature