Only worry re: fish is that the heat from the tegu enclosure might overheat your tank...keep an eye on that.
One way to avoid an overheat is to do the basking spot with halogen bulbs; you'll get a good hot spot but not a ton of heat going up to your tank. Argentine tegus (it's going to be an Argentine right?) don't need a ton of ambient heat, you can keep the entire cage heated to 80 or so and have a hot spot and you're good.
One way to avoid an overheat is to do the basking spot with halogen bulbs; you'll get a good hot spot but not a ton of heat going up to your tank. Argentine tegus (it's going to be an Argentine right?) don't need a ton of ambient heat, you can keep the entire cage heated to 80 or so and have a hot spot and you're good.