PAR Reduction from a Magnetic Frag Rack

[JohnNYC8]

If I were to install a magnetic frag rack in the top third of my tank would it drastically reduce low-tank PAR from light reflected off the glass? I have a 24” cube with a Gen 6 XR15 Blue and will have a 21” Blade Glow in the front to cut down on shading. I’m not PAR limited but I don’t want to create a lot of excess shading in one area down low.

I can’t seem to find anywhere how much reflected light actually contributes to PAR.

 

[bubbgee]

Having several racks on my frag/display tank, there is a significant reduction. My sandbed is around 250-275 but the ones covered by a rack is around 90 par.