Why supplement LED's with T5?

A few of the guys I buy frags from here locally all supplement their display tanks- which are primarily lighted with LED's- with T5's. I believe they are running 14k and 20k bulbs for two or three hours a day in addition to an 8 hour LED light cycle.

I'm not sure why this is necessary or helpful and I plan to ask them next time I see them. In the mean time do any of you have any experience or opinions on the matter?

I am running two Hydra's on a 48" long 18" deep tank half of which is newly heavily SPS populated so naturally I am concerned with ensuring that the SPS half of the tank is properly lit in the long run.

Any advice is appreciated. Thanks all.

 

Two things that come to mind would be:
A) the LEDs aren't full spectrum, so they use the T5 to cover the whole spectrum
OR
B) LEDs tend to cause a shading effect, due to the light being emitted from a single diode (though there are many diodes) where as T5 is a whole bulb so the light spread is continuous. So running T5 allows for more light to reach areas where the LEDs aren't.

All I've got at 2 am. lol

 

+1 to ^^^, although I believe #1 may be the main reason. A few companies had begun developing LED/T5 combo fixtures when LEDs were only available in blue and/or white; that trend appears to have been nixed now that other colors have been added to expand the LED spectrum.