I agree 5-6 leos is plenty for a 55 gallon.
So you'd need 5-6 regular hides, and a couple humid hides (if not one for each leo) so they can go in there if they want to (or a big one if they all get along).
Leopard Gecko's cannot see red, so I leave the red light on over my tank all day and all night and it keeps Phoenix's humid hide humid, it also keeps him warm. It stimulates his appetite and he has gained a couple of grams since I have gotten him which I think is terrific.
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2 Mali Uromastyx-Ares & Apollo
2 Bearded Dragons- Draco & Hades
0.1.1 Leopard Gecko's-Kalypso & Phoenix
1 Tokay Gecko-Sid Vicious
1 Tarantula-Peter Parker
1 Amazon Red Head Parrot-Pancho
1 African Gray Parrot-Keya
1 Dog-Cheeka
1 Zebra Finch-Beeps