Hi, First no matter what you decide to put in th etank, I would not use a power sun( if your talking about a MVB) on a 20 gallon long tank. Just to powerful, not enough distance away from basking site to be safe. Also there would not be too much of a temperature gradiant.

Either increase tank size to accomadate the powerful MVB or just use a uvb strip flouresant repti sun.

The tank could house a collared lizard, they are awesome, colorful, very diverse in pattern/color and get extremely friendly if handled best wishes with whatever you decide.

Let us know!

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PHEve / Eve