It sounds like what you are describing is an incandescent heat bulb. Those actually only provide some uva rays for the animal. What you need is a floroescent strip light bulb (i would go with the reptiglo 5.0) to provide the uvb your animalneeds. also, no the 75 isnt big enough to house your ig but it definately is an upgrade from the 40!
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1.0 ball python- Azazel
1.0 red blood python-Hiss
1.0 peach phase thayeri-Sancho
0.1 creamsicle corn- Pandora
0.1 partial stripe ghost corn- Raven
1.0 Sunglow motley corn-Ernie
1.1 hognose- Pricilla and Odd
0.2 leos- Boji and Kodama
0.1 beardie- Indie
1.0 BTS- Griffon
0.1 Iggy- Sunny
0.0.1 gray tree frog toadlet
0.1 pacific parrolet- Mishka
1.1 cats- Cairo and Oberon