Tank? Hehe... No tank... we're talking large enclosure.. 8 ftx5ftx5ft preferably if not bigger. Bigger is always better especially when housing 2 animals in the same area. As for basking.. try 130-140 degrees... What you listed is too low...and the cool end should get down in the 70's ideally. As for substrate... visually pleasing with a monitor is not something you should worry about. They're digging machines when kept properly. And that means lots and lots of dirt of proper consistency for their use. I'm still working on my dirt mix because my Sav still isn't happy with what I have her on...Its a continuous process that I've learned alot about in the last year.. but still have a long way to go. And I do mean a long way... While Savannah's may be classed as a medium sized monitor.. for their size they need large spaces because if they don't have excercise they get way overweight very easily and that could kill them. My Sav isn't exactly thin so I've had to cut back on her food intake...
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Lucien
1.1 Columbian Redtail Boa (BCI)(Sutekh and Isis)
2.2 Leopard geckos (2 Blizzards (Caine and Goliath), 1 het Blizzard (Lilith) and 1 Tangerine Albino (Tequila Sunrise ...Tiki for short))
0.1 Savannah Monitor (Kiros)
13 rats
1 Gerbil
2 Dogs (Loki and Storm)
2 cats (Sahara and Hercules)