any lower watt bulb can be put in a fixture rated for a cetain watt. What it means is the max wattage is 75. 50 watt would be better but to get an exact idea you will need to monitor it yourself. Put a ther/hyd meter in the tank below the light to know exactly what you are getting from it. Dept of substrate, room temp , placement of light, All of these will factor what temp and humidity you get.