I am using a 10 gallon tank for my two American toads ive been keeping it outside since they were yearlings but its getting cold and I found an old natural daylight 15 watt bulb that fits perfect on top and I was wondering if it would be okay for my toads and their moss...they have plents of shade places in the tank and I was wondering if I could use this bulb until it goes out and after that what kind of bulb could I buy to replace it...the bulb has to have two prongs on each side and be 18 inches long...the lamp says 120 vac, 60hzz, 17w and its UL.....