For a 40 gallon + tank you want a 24 watt Arcadia Pro T 5 w/ a 12% bulb --- if you have a Pet Smart where you live check there or see if you can order it on line from Pet Smart -- or this one
24" Zoo Med w/ a Reptisun 10.0 T 5 bulb
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this will come w/ a 5.0 bulb keep it for a back up --- distance and placement is different from the bulb you want
22" Zoo Med ReptiSun 10.0 UVB T5 HO High Output Fluorescent Bulb
when you get the UVB please post back on here so I can help you place it for your tank --- distance and placement will be determined by your screen on the tank