I just rented a par meter from BRS and performed this test. I have a DD Jumpguard Pro on my 225 gallon. The netting is black. Not sure if clear would make a difference... When shopping for a guard I read clear causes more reflection vs black however I don’t know the accuracy of those comments.
I took readings with all pumps on peak day flow settings. Dual COR 20 returns, 3 Red Sea Reefwave 45s & 2 MP 40’s. With the lid on I saw about a 50 par drop average vs without the lid across the tank.
What’s really interesting is to see the constant change in par because of water movement. It really jumps around, I was getting 25 to 75 difference in par within 30-40 seconds.
I ended up taking readings for 30 seconds plus in each location to get an average of the par.
Hope this helps!