A regular household light bulb is fine for a basking light if you also have a UVB light such as Reptomin 5.0 or 10.0. The wattage of that basking light depends on how large your turtles are and how far away the basking spot is from the turtle. For larger turtles or longer distances, a 75 or 100 watt bulb might be better - measure the temperature on the basking spot to be sure.

Katrina
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1.2 Eastern Muds - Fred, Ethel, Edith
0.1 Iguana - Tiffel
Foster turtles: More than I'd like the husband to know about.