I wouldnt try clams with it.
Measuring lumens is just part of the advert for the brightness in output. This has nothing to do with the spectrum or ratio of usable lighting from a given source.
Kelvin temp or color of the light is what matters first. Lower K like 3000k or 4000k is what is common in Halogen and Bright light bulbs for your home. This WILL be usuable light for corals but will be MUCH more usuable by algae and it will quickly overrun the tank making it a very poor choice.
Coral can adapt and use many different spectrums to feed but depending on the source of this light the PAR value or how true to spectrum the bulb can be substantially different from one bulb to the next depending on manufacturer and also from method to method in delivery. All the factors make is seemingly intentionally more difficult by the manufacturuers to tell when your really comparing apples to apples.
This is how smaller wattage bulbs out perform vastly larger wattage bulbs and lighting systems. I read the same articles as others but unfortunatley I am stubbourn in my ways and MH have worked so well for me I am resistant to run anything else.
So when people talk about growth many jump to blurt Lower Kelvin.10k!!. True sunlight at noon is said to be around 6780k so often this is thought of as "Best" but best is in the beholder. Higher spectrum bulbs tend to have lower par value so same manufacturer and same wattage bulb, but change the spectrum and the PAR changes. The growth rate is cut in half by in most cases just by switching Kelvin.
I wont try to corner the market in a template showing all the different values of all bulbs and all the various companies that swear thier bulbs are the best.
Flouresents (common) aka T12's and T8's
Thier lumens are usually pretty good but the PAR is real crap on most of them, to break 75 on a "daylight" bulb is hard for them to achieve, This is why you could add 200watts of common flouresent and while lumens are good the light is just not clean nor usable in proportion to the output in terms of staying true to the wavelength.
Compact Flouresent- aka PC, swirly bulbs included
They have much the same characteristics as normal flouresent bulbs but they can fit in a smaller pace and they try to make up for thier lousy PAR by being compact and thus giving you the ability to pack more wattage to try and make up for it. They also are generally available in more color(kelvin) choices making them more of choice for this hobby.
T-5 aka mini Flouresent
These are not NEW to the market as most people think but in the past they fell short of delivering true usable light as the manufacturers promised. This has changed in recent years in two ways. Name brand makers have been able to get better quality and more juice into tighter spaces while keeping a relativly good par ratio. The cheapo ones are still out there giving the good a bad name but they will indeed become more and more popular along with this latest craze in the hobby, once the hobby meets up with the drive for greater and greater efficiency.
MH- I wont get into MH as it is a bit of a dead horse.
Its nothing but a glorified shop light. It is just available in the proper K and good PAR so we flock to it for its proven results.
Intensity- Shallow tanks it becomes purley about personal choice. While the above lights, yes any one of them in my opinion will do great with even clams and SPS. You might have to run a bank of 50 regular flouresents, or 10 Compact floursents they ALL will work to feed a photosynthetic organism. Size and configuration and Kelvin availability might get in your way. Not to mention the power you would be pumping and wasting to try and compensate for inferior PAR values of given methods of delivery.
DEEP tanks-
The saying theres no substitute for Cubic Inches holds true when your talking about penetration. (wow sounds dirty)In deep tanks like 36 and 48inch deep reef tanks, the water itself will disperse the lightwaves and spread it into unusable light so MH is the crowned champion. A bank of 400w MH in action can put the hurt on a anything craving light even at very deep relative depths. This is where wives tales and stubbourness is born, myself included, once you run a large tank for a while with MH you just see all other lighting as a pale attempt at what MH can do in a single bulb.
Now I have gotten WAY off on a tangent but the original question- can I use the swirly compact bulbs for coral?....
Yes but its really a poor mans light. they work great for fuges since the 6500k spectrum is good for algea. I just put one on my new nano in fact, but the color washes the tank out and often makes it look drab. The other factor is dont be fooled by the Advert that states 26watts. That doesnt mean much when its output would be around 1/2 the amount if in T-5 and 1/3 the amount if it were MH.
Thats my .02....or rather 2.00 as much as I rambled. Sorry for uch a rant.