How much MH light lost to 1/2" acrylic tank top?

[plankton123]

I have a 100G acrylic tank that does NOT have euro bracing and does have a 1/2 inch top with center brace. Question is if I install a halide in the middle of the tank (currently have two on each side) how would the 1/2 " acrylic change the intensity and spectrum reaching the water?
Anyone done any measurements with a light meter, etc?

I already know that if any salt spray collects on the center brace then the intensity hitting the corals will drop off like crazy.

Thanks.

Scott

 

[Anonymous]

hi.
Acrylic is so clear that you can see thru 8 feet of it without problem. For 1/2 inch, the modulation is almost neglectible. So don't worry about the change in intensity or change in color.

The main concern is that if you place your MH too close to the acrylic sheet, it may soften. Minute crack and deformation are indications that you are placing it to close.

 

[plankton123]

Seven,

The halides are about 8" above the water surface, 7" to acrylic. Fans blow air across the tank surface between halides and top of tank. Thanks for the warning regarding acrylic possibly softening up or cross polymerizing. I'll experiment by adding an extra piece of 1/4" acrylic to see if it:

- reduces light level
- reduces heat buildup in center brace.

PS Next tank will have edge bracing with no center brace!

Scott