Hydra 52 26 HD colour differences between lights | D-D The Aquarium Solution
Question: 

Hi
I’ve just purchased a new hydra 26 HD... I’ve put it along side my old one on the tank and there’s a noticeable colour difference in the blues.. has the LED’s been changed on the newer models?
Secondly on my old hydra 26 HD the lenses have melted under the UV LED.. is this a known problem and can the lenses be replaced?

Regards
Leon

Answer: 
Dear Leon
 
LED diodes are produced in batches or otherwise known as ‘bins’ . No one batch will be the same as another as by its nature the production process of LED diodes wont be able to replicate the spectral output of one batch to the next . Cree one of the largest and most respected manufacturer of LED diodes quotes an acceptable threshold of +/- 7% between batches. 
 
 You will find Cree LED’s in most high quality aquarium lights as well as other high end LED products. If one were to buy 2 aquarium lights at the same time one would confidently expect the spectral output of each channel to be pretty similar visually but of one were to purchased lights from different manufacturing periods of say the initial run D8976001XXXX and D8976004XXXX you will have a much higher chance in seeing a difference in output based on the fact that all of the LED’s in both lights will have originated from different Bin’s.
 
However the human eye will not neccesarily render the slight differences correctly due to the way the cones within the eye detect certain colours so the shift can be exaggerated but in testing will have very little to no difference with regards to available photo synthetic radiation levels for the coral.
 
You may find the following article of interest
 
 
With regards to the optics showing signs of melting, this isnt normal. How close to the water surface are the lights and is there a cover glass beneath them?
 
Best regards Tony