Sproket:
To my knowloedge D-tek has only one heatercore. Some painted and one unpainted. Mine's black and I have the barbs screwed in. My pump is an Hydor L30.
The UV dye is not Dye-Lite nor comes from D-Tek. We deal with an industrial company that makes UV dyes, UV paints and UV inks among other things. They know their stuff when it comes to UV. I honestly know no other stores that uses that company. I'm not saying we are the only one but I haven't seen one that uses them yet. Most use Dye-Lite and brand them under their name.
I'd like to help clear this matter out for you so if you pay for the shipping I'll send you a 1 oz. bottle for free.
Try it out and then we'll see if ours does the same thing in your system. If it does then we will know that no matter what type of dye you use something in your system makes it fades really quickly.