Par rating through lid?

[Mattyice572]

so i cant find any information on this, maybe someone can help me. Saw a BRS video today about par rating loss through a mesh screen top which claims you lose between 2.5%-6% par rating depending on lighting. This is a very minimal loss and is acceptable in my opinion, however i was wondering if anyone is using clear corrugated plastic as a lid and if so if youre having any negative affects with it, or even a glass top. I was hoping to get an actual lid vs this mesh screen too to cut down on evaporation. I have a 90 gal reef that im just setting up and am running 2, ai 32hd lights and am planning to keep an sps reef and if theres more negatives to using a glass top or plastic lid id rather just deal with the evaporation. Any feed back is appreciated! Thanks!!

 

[reef3reef]

I use a plexiglass sheet as a cover. There is an approx 10% cut of par if the plexiglass is clean and free of condensation. However, as soon as you put it on, condensation will start forming underneath, which can cut your par by 30% or more. Note these numbers are all approximate. I just boost the light by the same amount. Even so I still prefer it because it keeps the dust out and slows down evaporation. Also, plexiglass (or other plastics) will sag so take that into account when designing your lid.

 

[AquaBiomics]

Thin glass lowers PAR by about 5 to 10%.

 

[oreo54]

so i cant find any information on this, maybe someone can help me. Saw a BRS video today about par rating loss through a mesh screen top which claims you lose between 2.5%-6% par rating depending on lighting. This is a very minimal loss and is acceptable in my opinion, however i was wondering if anyone is using clear corrugated plastic as a lid and if so if youre having any negative affects with it, or even a glass top. I was hoping to get an actual lid vs this mesh screen too to cut down on evaporation. I have a 90 gal reef that im just setting up and am running 2, ai 32hd lights and am planning to keep an sps reef and if theres more negatives to using a glass top or plastic lid id rather just deal with the evaporation. Any feed back is appreciated! Thanks!!

My "go to" article ..;)
https://www.thekrib.com/Lights/lights-wozniak.htmlPre-"PAR"
https://www.sciencedirect.com/topics/chemistry/plate-glass
One thing to note.. plastics generally have an abrupt cutoff in light transmission around 400nm..

Glass: