I'd still try the fixture closer. If you make it 6" you roughly double all those numbers.
Unless you can think of a reason not to, like I said already, I'd try the 250w light too since you have it. (Don't make a problem for the return, of course.)
Just got home from work and my first impression of the corals in the tank is that they absolutely love the MH lighting... All of my corals are opened up bigger and better than ever. My clam is also more opened up than I've ever seen it [even counting in the tank I bought it from.
I tested the 150w [phoenix 14k] at approximately 7" down from the bulb [didn't actually lower it, I hung yarn to 7" and gave it my best estimation].
I got
150w MH
7" under source
Rear of Tank
25k 25k 25k
33k 38k 38k
20k 21k 21k
18k 14k 17k
Front of Tank
Testing the 250w [stock 15k?] with the meter, this was much more difficult since it wasn't over the tank and I was guessing at distances compared to where the tank would be underneath the fixture:
150w MH
7" under source
Rear of Tank
70k 75k 68k
82k 100k 80k
68k 65k 67k
100k was the highest value I got, whether I went from 7" underneath the center, or directly underneath the bulb. My Lux meter's highest setting is 50,000 and it multiplies the value by x100 to get the LUX reading, so it's possible that my meter isn't accurate enough at these ranges?
I saw that Salty posted in another thread about conversions from LUX to PAR [roughly] suggesting that MH LUX readings should be divided by a constant of 50 for a 20k Radium. I'm running a 14k Phoenix though, so not sure if it's helpful... Regardless,
PAR converted using 50
150w Phoenix
500 500 500
660 760 760
420 420 420
350 280 350
At the water surface, this doesn't seem like enough for a SPS, clam and BTA dominant tank?
The tip of my tallest coral is an additional 4" under the water line, and the rock is 6" under the water line
the 250w stock bulb with 100k LUX in the center though would come out to 2,000 PAR at the water surface, mounted 7" above the water line. This seems like too much for a lot of coral [maybe not clams once acclimated though?]
The other LUX points from the 250w come out to around 1,200-1,400 par at the water surface across the tank without using the T5's, which would be used only for dusk/dawn, not full lighting periods
Can't tell you how much I appreciate the continued effort and assistance!