The watts per gallon rule is *general rule* or gauge.
One need to decide what species/ genus they plan to house. The hobby has made it relatively simple when it comes to habitant keeping.
No light coral
Low light coral
Medium light coral
High light coral
When you decide what coral you want to keep you base your lights off those decisions.
A lot of keepers choose to go with metal halide lights, why? Because they are not limited to coral/inverts species they can keep.
While yes you can achieve the same WPG with “T” bulbs there is the pros and cons, same with Mh lights.
If you wanted to not be bound to certain coral then 5-7 watts will suite your every need and desire. You just need to deciede what and how your are going to achieve those watts.
To “measure” lights that suite your tank ,you are getting into a heck of a mathematic headache.
I went as far as to by a Lux light meter. The only thing the lux meter is good for is???? To tell me when my bulbs are getting weaker at the lowest point in my tank, that and proving to my fiancé that I am an addict and spend way to much money on my systems.
On the simplest terms and the most easy way to figure it out.
For metal halides you will need 1 pendant for every two feet of tank. I.e 48 inch tank would need two pendants.
For depth
18inches deep needs on or about 175 watts.
Up to 24 inches deep 250 watts.
These are some of the “general rules” you will see often enough.
For your tank, if it was me personally, I would run 1 250 watt Mh light in the middle of the tank 10K or 12.5 (love 12.5k) with two 95watt VHO act 03 lights on the front and back side.
That would 6.875 “watts per gallon”
