I used to have a six foot long iguana in great health .... so when I lecture, you'll know at least I know what I'm talking about.

First of all, iguanas need a LOT of room. My iguana, Willie, had a cage that was six feet tall, six feet long and three feet deep ... plus he had the run of the living and dining rooms most of the day.

Second, green iguanas (which is the most common pet store species, and probably what you have) are tree dwelling lizards. This means that you must have branches in the cage for him to climb up onto. Green iguanas do not do well unless they can climb.

Third, diet is the single most important, and single most botched, aspect of iguana care. Poor diet kills almost all captive iguanas by the age of three ... when actually their lifespan can be over fifteen years! Calcium deficiency is a huge problem. However, it is not as simple as just supplementing with calcium. The supplement must contain the correct ratio of vitamin D/phosporus/calcium. If it does not, the calcium becomes indigestible, and you have no gained anything.

Fourth, NEVER put a heat rock in for an iguana! Heat rocks are for ground dwelling reptiles, that warm themselves by laying on rocks that have been heated by the sun in the wild. Tree dwelling reptiles, like green iguanas, do not lay on hot rocks in the wild, they sun themselves in direct sun on a tree branch. Iguanas get their heat from above, not from below, in nature. Why does this matter, you may ask? Because a ground dwelling reptile is evolved to lay on hot rocks. Its digestive tract is higher up in its body, away from the heat source. Tree dwelling reptiles are evolved to bask in the sun on a tree limb. Their digestive tract is lower down in its body, right on its belly, away from the natural heat source. By forcing an iguana to lie on hot rock, you are putting all the heat right on its digestive tract. This cause the food to ferment before the helpful bacteria in the gut can digest the food. This can kill your iguana, either from malnutrition, or from food poisoning. Get that hot rock out of there, and put in an overhead heat lamp.

The best advice, frankly, is to go buy a detailed iguana care book. A good one, not a little pamphlet. Read it cover to cover, and then read it again. Highlight it. Memorize it. It will tell you all about food, supplement, housing, heat, illnesses, etc. You cannot raise a healthy iguana without one.

And, take your iguana to a herp vet, asap.