jack, sally, and zero

Question
Hi my names Jordan and I bought a 75 gallon tank for two schneider skinks and a butterfly ogana. Yes they can co exist together. Both completely docile. Theyre in a 40 breeder right now and have a 100 watt for them and theyve been thriving. sooo i was wondering about the wattage for my 75 gallon. its a desert terrarium and i have an undertank heater and already bought a mercury vapor bulb 125 watt. i figured that would be good. its a couple inches taller than the 40 and they have plenty of room to thermoregulate. Am i right?

Answer
Hi Jordan,
The species you mention are outside of my knowledge as to in depth care but as to the wattage needed, the answer is what ever wattage is needed to get the temperatures that is needed for them.  
It will depend on season, room temperatures, humidity, air circulation in the room, etc.  Basically, you need to play around with different wattages to find the wattage that is needed to get the required temperatures.
I believe both species need to have a basking area of around 95 degrees, with ambient temperatures around 88 degrees and a cool area of low 70's for during the day...night time, their temp range is upper mid 60's to low 70's.  
Its important to measure the temperatures correctly. The recommended way is right where the reptile basks, at their level. Recommended is a thermometer with the wire with a probe on the end, which the probe is placed at the reptiles level, in the basking area.  The main part of the thermometer can then be placed in the ambient temperature area of the tank.  One of the easiest ways to spot check your temperatures is with a temperature gun.  ( www.reptileuv.com )
A 125 watt should be more than enough to provide a proper basking temperature....but my thought is that the 3 lizards won't have enough room in a 75 gallon tank and all be able to get 12 hours of needed uvb. If I remember right, at least a 50 gallon is recommended for 2 skinks.. and the agama needs to have about the same size.  
With the MV bulb, I'm not sure that brand have been independently tested as of yet,(for life output of good uvb) but they do need a distance from the reptile of 12-14 inches.
Since most, if not all butterfly agamas are wild caught, they generally have a heavy load of internal parasites.  If you haven't done so, I do recommend that you have all 3 lizards tested for parasites.  As to housing together, many times, its not an issue of them having the same care needs or getting along...many times its due to some species carry diseases that to their own species isn't a problem, but to other species can be deadly.
I'd be interested in knowing if your skinks are eating some of the fruits and veggies that your agama is eating, along with the insects.