They also have seriously different dietary requirements.
WD's need insects in their diet while an iguana should only be fed plant material!

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Merlin,
What's Life Without A Little Magic!

What's the difference in care, though? Aside from the diet, I don't see what is different between the two. I've never done it myself, so I'm not saying I'm right, but I just don't see why it's impossible. I hand feed my WD, so making sure the WD eats what it should and the Iguana eats what it should, shouldn't be an issue. It sounds like Metabolic Bone Disease might be an issue, but if the WD is eating, it just means he/she isn't basking under enough UVB (Which could be territory issues), which could be fixed by placing another lamp inside the enclosure. As long as the two aren't fighting, which the OP didn't suggest any issues with, I don't see why it can't happen. If lizards can become tame to human touch with a couple hours of handling a day, I don't see why lizards can't become tame to each other when they live 24/7 together. Although was the size of the enclosure ever mentioned? I'd imagine that would play a lot into it.

One of the main hazards is the fact that water dragons are from Asia and iguanas are from Central and South America. There are diseases and parasites that are part of their native background that may have absolutely no affect on them because they evolved in the presence of these organisms, and as such are immune. While the other species having never been exposed to them have no such immunities.
Also iguanas are much larger, stronger, more aggressive and territorial than WDs. They will also grow at a faster rate than the smaller dragon. Within a year the iguana is going to outgrow the WD. If it hasn't already killed it.
Dominance stress doesn't mean they have to be physically fighting for it to exist. Just as an example,...
Imagine that I am twice your size. You spend all day with me hovering over you, glaring down at you and you are afraid that at any given moment I am going to jump on you and beat you up and maybe kill you and eat you!
Now imagine the two of us are locked together in a phone booth 24/7with no avenue for you to escape if I do decide to kill you.!
Not a very comfortable living arrangement!
You are thinking in human terms, not like the lizards! Because socializing a lizard doesn't happen in just a few days and can take up to a year at times. Because in order to tame a lizard we go to extraordinary lengths to teach it that we are not a threat. We move slowly, talk and handle gently, hand feed, and do everything we can do to socialize it. It is an initiative that WE as the keepers take.
A reptile will not think in these terms. As far as they are concerned its a matter of I want to eat,... I want to breed,....I want to bask,....
Now get out of my way or else!

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Merlin,
What's Life Without A Little Magic!

I'll agree parasites are bad in any case. And I agree that aggression between the two can cause stress. But there still isn't a gaurentee of aggression just because of the size difference. You're saying the meer presence of the lizard is enough to cause stress, but what I'm saying is after a while the WD will be used to the presence of the iguana and won't become stressed. If the WD is still eating fine, it probably isn't too stressed because that's usually the first sign, lack of apetite. I still think, IMHO, if an owner wants to keep an iguana and WD together, it's possible. They enclosure will have to be big enough and it's very important that special attention is paid to ensure they are both eating and basking properly as well as looking for signs of aggression between the two and especially wounds. But I don't see why the two living together is seen as an impossibility and taboo.

I have to disagree, JD. I'm sorry. I've had both a water dragon and iguanas. The care I gave them was extremely different. Beyond temperature and humidity differences, which are minimal, they are extremely different in size a temperament.

Iguanas are usually pretty aggressive creatures. Even "tame" iguanas (keep in mind that they NEVER actually tame. They tolerate you, but they are always going to stay wild animals, and therefore somewhat unpredictable.) need to be watched for signs of aggression. They tend to be more nervous anyway, and that reflects in their behavior. They're vegetarians - which also means they are prey. They are also extremely sensitive to hormone changes in humans, which upsets them and makes them act out even more.

Water Dragons, on the other hand, are predominately predatory. They eat insects and small rodents - along with some veggies, sometimes. In my experience, they are much less nervous and edgy - thus, much less aggressive. I've never seen one respond to changes in my mood, attitude or hormones. Of the two, water dragons are much more stable creatures.

However, this lack of aggression in general would prove deadly if kept together with an iguana. Like Merlin said, the iguana will grow faster, and much bigger than the water dragon. The iguana is also much more aggressive. Both species are also territorial - which leads to problems even within their own species. Some iguanas will not even tolerate a mate in their territory. And their territories can be very large. I'm not sure even a room sized enclosure would be enough to keep two male iguanas from ever fighting. Simply having more space would not solve this problem.

Water dragons, too, are territorial enough that you cannot house two males together without the possibility of them fighting. Neither species ever gets fully used to another reptile in their space, even if they were born and raised together. Because a healthy water dragon will always be smaller and less aggressive than a healthy iguana, you can pretty much expect the water dragon to get the worst of it - and likely that will result in death, either from fighting or from being dominated into not eating.

I think a huge part of why we don't recommend housing these two species together is that we don't recommend house two of the *same* of either of these species together. It's dangerous to the animal. And while there's always a chance that it *might* work out okay, it's not likely, and certainly not in either animal's best interests to experiment with.

On a another note, since I've had both, I know that my approach and care on a personal level (such as socializing) is extremely different. What a dragon tolerates beautifully, can trigger an iguana's aggression. Treating them both the same, is treating them unfairly. My opinion only on that part, though.

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"Let's eat, Grandpa!"
"Let's eat Grandpa!"

Punctuation. It saves lives.

Fair enough. I'll take your word for it since I've never had an iguana.

Tiff is correct, care is different. No way could they be kept together.

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MARSHA
A man without a woman is a bachelor, A woman without a man is a genius!.

We have enough youth, how about a fountain of smart!

Perhaps, if we have not chased Tiffany away - she might get back with us in the near future and advise as to whether her WD has survived the every so bullysome and prying eyes of the hovering iguana? I have to tell you all that I love this website for so many reasons (give you three) - 1) being that you get such wonderful information from knowledgable individuals with experience - 2) it can be so darn entertaining... it reminds me of talking politics at lunch with my co-workers, we all certainly get passionate about politics (and apparently our reptiles) - 3) Merlin can be awesomely scary sometimes and I love it! Merlin, do you have such magic with seemingly deaf and unmindful teenagers? Much love. :0)

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~ Jess ~

LOL! Well I did raise four of them myself!
Didn't have to kill a single one of them!
Though there were times,.....

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Merlin,
What's Life Without A Little Magic!