Just a FYI. Temp and tank lids.

I agree, I have a 500w for my 90.

 

I second that. I have a 150w in my 30 gal.

You ideally want to go big when getting a heater, definitely if your room temp will fluctuate significantly.

If you don't have a backup heater in the tank, have one on hand.

A simple digital thermometer with an alarm for a high water temp and low water temp is a must if you don't have a tank controller!

 

I have a 300 watt heater on my 58G total volume. Gets down to 68 at my place at night. The 150w could not keep up.

That tank looks like a 55 or 90 to me. I'm guessing a sump or something below adds the rest of the volume.

I think 6" means its just 6" to the side laterally - pretty direct air bombardment.

Why would you leave it on 24/7 though? Seems like a waste of energy, but not my business

Agree a glass lid will impede gas exchange, but a good skimmer should easily compensate.

Personally, I'd just like to see a better shot of that wall art on that door. 8)

 

Ditto!

 

Appears you all are right. I'll get a nice 500W heater. Any suggestions? I don't have a reef controller yet. Preferably digital or one I can adjust without reaching inside the sump.

Here are tank dimension I took, and entered them in a Calculator.

You provided measurements in inches:
Width: 48" (121.92cm)
Height: 21" (53.34cm)
Depth: 18" (45.72cm)
Your tank's volume is approximately 18,144.0 cubic inches or 78.5 U.S. gallons, which is approximately 305.5 liters.

Then there is a 30 gallon sump underneath. More graffiti pictures as a reward for you helping me