perfect and thank you!Pet Smart carries the Arcadia --- you want the 24 watt 12% bulb --- those are made in Germany so they go by the %'s of bulbs they make different ones - the Reptisun are made in US and go by watt and they are 24 - you have T 8's that most of the Pet Stores carry you want a T 5 for a 120 gallon tank - the T 8's are not as strong -- place as close to the basking area as possible it needs to be in the tank and directly over the basking decor piece 12-15 inches - change the bulb out in approx 10-11 months from date of install