Depending on the locality of the mangrove,most of the animals imported to the U.S. only get about 3 to 3.5 feet.Some do get bigger but it all depends on where they where collected.So you cage should be fine for now,but I would go bigger.These guy are not the easiest monitor to care for.They don't take well to captivty and most will fail in the fist year.One of the biggest problems new keeper do with these animals,is they fail to offer security.These guy don't like being seen and need to be given the ability to move about the enclosure and bask with out being seen.They do not take well to handling and the stress from it could kill them.The need a hot and humid cage,but they have thin skin and are prone to fungal infection if kept too wet,so you need to know the difference between humid and wet.Most new keeper struggle with this and even old timers do as well.I still have problem with it.I still do not understand why you went with an Indcus instead of a roughneck.The roughneck would have been far more rewarding as captive.All in all The Indcus complex suck as captives.Most people who keep them myself included will tell you keeping them is like feeding a cage.

Could you post some pictures of your set up so we can help get you going in the right direction,plus I love seeing pics of the Inducs complex as the are the best looking monitors out there IMO

Greg