Don't know about the gerbils or the best place to get a thermo/rheo stat, but your snakes do need a small drop in temperatures to simulate night time, only about five to ten degrees. Doesn't stay 80 degrees at night in Africa 
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1.2 normal ball pythons (Cindy, Darwin, and Periscope)
0.0.1 california kingsnake (Tetris)
0.2 rescue chinese water dragons
1.0 rex rat (Scurvy)
1.0 gerbil (Yerbul)
0.1 bunny (Spazz)
1.1 betta fishes (Vicious and Killer)
2.2 great danes (Shasta, Odysseus, Merlot, and Watson)
1.0 fat fuzzy mutt (Smokey)
1.1 cats (Thidwick and Turtle)
2.0 horses (Buddy and Sam)
1.0 goat (Billy Jack)
1.25 chickens (Ugly the rooster and his harem)
"God is a comedian playing to an audience too afraid to laugh." - Voltaire