Lighting Through Glass

How much light do you loose by having a glass splash guard? Would using acrylic be better?

 

From what I can remember you lose about 30% going through glass..

Acrylic is much much much less. It would make a much better splash guard, but you have to remember to keep it clean. You won't lose much light through the acrylic but let it cover up in salt creep and that changes quickly.

 

Light gets filtered out by glass. Acrylic would be better, depending on the light source. If you are using T5HO or MH lights, or even Compact Fluorescent, heat could cause the acrylic to warp.

 

+1 Point taken. I'm doing a DIY hood with actinic/daylight PC's and 150w MH on a 36gal bow. How high do you think they should be above the water level?

 

One thing to keep in mind that glass & acrylic both reduces the oxygen transfer that occurs with surface aggitation. Open top or some sort of pourous cover is much better.

Egg crate is an option possibly depending on the type of fish you want to keep.

The best option is probably a netting lid cover. There are quite a few threads here on how to build them. Basicially like building a screen window.

Quick plug: BRS (site sponsor) sell the mesh netting. I bought some but I still have actually building mine on the list of things to do.

 

Then would you just suggest putting an acrylic cover over the lights on the hood and adding fans to draw the heat away so the acrylic won't warp and leaving the water uncovered (barring the addition of jumping fish)?

 

If it's clean virtually none. Many people quote 30%, but this is crud. I think maybe people are using LUX or theoretical considerations or something. Or regurgitating made up things they've heard LOL.

A relative of mine had glass tops over the tank, and I tested the PAR. Even with somewhat dirty glass (i.e. salt creep), the PAR less than 10%. With clean glass, it was less than that (IIRC where i measured it went from about 177 to 170).

Melev also did a similar experiment here, with similar results (around 1/3 to midway down the page, he tests 1/4 glass and acrylic):
Melevsreef.com - PAR Measurements Taken

"While I was at the glass shop on Friday, I brought home a piece of 1/4" glass that is 20" x 20". This was placed on top of some acrylic strips spanning the tank, putting the glass squarely beneath each bulb. PAR readings were taken to see how much light the glass filtered out. Because the glass was essentially in my way, I used the acrylic holder to hold the probe 12" directly beneath the bulb, and took only one reading. There was very little drop off in PAR. "


HOWEVER that said, you should not use either glass or acrylic! I did loose a number of fish once when the return line came off the overflow, on a tank with a glass a canopy. The glass prevented O2 exchange, so, all of the O2 exchange was occurring in sump and protein skimmer. When the sump became disconnected form the display, all of the fish suffocated! USE SCREEN TOPS! I can't stress that enough....

 

I have Panorama Pro modules which claim to be water proof, should I go no cover then? I'm always having to clean my plastic splash guard from salt creep and often I forget, then eventually I remember and it's very very crusty and foggy

PS-

These screen guards look nice but basically isn't it just chicken wire? I can see that being useful for fish jumping out but what about as a splash guard?

I guess that's why I'm wondering if it'd be okay to just remove it completely so my LED's get ultimate light penetration and I don't have to clean salt off my plastic guard every 2 weeks

 

I wouldn't worry about a splash guard. I'd remove it if it were me.

 

But my tank is a 29g Biocube so that mean's we're talking about less than 5" of space between light fixtures and saltwater. Still think I should remove the splash guard?