Seconding just lowering settings.
Probably plan to eventually swap it out with something smaller and repurpose the XR15 if you want - that tank realistically doesn't need but about 20w - 30w of lighting or so.
I have a NooPsyche K7 Mini @ 60w over my 14g 'fuge, and I don't expect I'll ever run it at much more than 30%.
Bonus though, the less power you run through the LED's the longer they will last before they start to dim and shift spectrum.
And YES, LED's do not last forever... or even as long as the diodes do. Even though the light is on doesn't mean it's providing the same total output or spectrum it did when new, and your eyes will not be able to tell the difference. If you run them at 100%, most are only good for 2 - 5 years (depending on the original quality) before they can stand for replacement, but lowering their output can definitely extend their useful lifespan.
