I was planning on getting a capture the sun mercury vapor bulb from www.bigappleherp.com

They come in 100 watts and 160 watt bulbs. My tank is a standard 55 gallon aquarium; which wattage do you think I should use. I understand that temps vary depending on how close the basking spot is to the bulb, and the beardie's basking spot would go no higher than half way up the tank.

Also I was wondering if anyone has used these bulbs and if they would recomend them. Thank you.