The below method is my method for introducing a new tegu and may or may not work for you. I am a bit overly cautious, but to this point I have never had a tegu of mine die or get seriously injured. When you attempt to house two large animals together you take a risk. I can not be held liable for any method you may attempt to do.

I start by introducing the new tegu to the established tegu on the floor in a mutual area, such as the living room. While doing so I wear leather gloves because if they start fighting you may need to get involved and you don't want your bare hands between two fighting tegus. I watch them carefully on the floor for a few minutes to an hour, time depending on what I have to do that day. If they ignore each other, lay together, check each other out and walk off.. then it's a good session. If they start quick tongue flicking I get up near them, ready to react. This does not always indicate something bad is about to happen but I like to play it safe.

I do this for several times during a week. I never leave them unmonitored, not even to get a drink or go to the bathroom. One week two I do the same thing.

This time I do it from outside of the room. Giving the tegus more space and privacy. After week two, I feel pretty secure that they tegus are fine on the floor together, but there could still be territorial issues in the enclosure, this is very common.

On week three, when I have a full day to use, I pull everything from the enclosure, empty the used substrate and clean everything, the inside of the enclosure, the decorations, the water dishes, the plants, etc. I then add new substrate. Replace the hides, decoration, plants, etc. I put everything in a new location to make sure nothing is the way it was prior. With leather gloves back on and with every door to the enclosure opened, incase I need quick access, I place the new tegu in from one side and the established tegu in from the other side. I try to place them both in at the same time.

To both tegus this looks like, smells like.. thus it is; a new enclosure and neither one 'owns' this enclosure. It is theirs. This works for me to keep territorial issues down. I sit right there and watch. I watch them carefully for the whole day. In the evening they will find a corner or dig in and go to sleep. At this point I leave them alone, but I check back in often. In the morning I watch and wait for them to start moving, normally between breakfast and lunch they start waking and exploring. If all goes well today, I will likely have success.

Note: Before trying to introduce any new tegu a strict quarantine should be adhered to. A health tegu from someone you know could still carry parasites that will make sure tegu(s) sick. Even a health tegu, who has normal flora/parasites inside it can have its immune system weakened by the stress of moving and can become sick for apparently no reason. Give the tegu time before tossing it in with your healthy tegus.

Rick