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Discussion Starter · #1 ·
I built my own light fixtures and want to raise them above the tank then remove the glass lids on the tanks. Just wondering how plexiglass will hold up to the heat of 4 36" T5HO bulbs?

What allows better light throw glass or plexiglass?

Don't really want a bulb to break and end up in the tank.

Thanks,
Matt
 

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Not sure how plexiglass would hold up to heat but getting the calcium build up off of it would probably be a nightmare. Have you considered going open top and hanging the light or putting it on legs? Open top allows maximum light, ease of maintenance but you will have more evaporation. If you go open top, remember using a GFCI outlet or strip. You don't want to zap yourself.
 

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Discussion Starter · #3 ·
I'm going to go open top, but worry about the bulbs breaking and ending up in the tank. So the plexiglass/glass would be attached to the light fixture. Just wondering which would be better.
Any other ideas on what to put on the fixture to keep the bulbs from landing in the tank?
 

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T5HO bulbs don't get that hot to worry about them shattering from splashing in my opinion. I too use 4x39 watt T5HO bulbs without anything covering the bulbs. The fixture is maybe 6 inches above the water line on legs. I regularly stick my arms in under the lights when they are on without incident. But, it is attached to a GFCI outlet. This is probably dumb but, I have been doing this for over a year.

That being said, I would use glass over plexiglass.
 

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I have built a couple of fixtures using Plexiglas (acrylic/lexan) sheets attached to the bottom. Here is an example: http://www.plantedtank.net/forums/786667-post84.html

It works well for me. I use active cooling (fans) to keep the temperatures down. So the heat isn't an issue.

I find wiping them down with a vinegar/dish detergent solution to clean them once a month isn't a big deal. If they get too yucky, simply replacing them is easy.

Only issue is the price... as long as you stay below 4ft it is alright, but larger sheets get really costly. Price is also a function of thickness of course, the thinner, the more they need to be supported. I simply use some long screws in the center of the sheet to keep them from bowing.

Compared to glass, they are lighter (big plus), easier to cut (big plus), unbreakable (big plus) and a bit clearer.
 

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Discussion Starter · #6 ·
I have already had one bulb break from over heating. At least that is what looked liked happened. I plan on adding fans on each fixture though. Currently the air is drawn across both fixtures.
hbosman: do you have fans to cool them?
 

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My fixture only has one small fan that blows are out of the back so its only good for cooling the ballasts. Now that I think about it, it did come with a plexiglass shield but, I removed it because the bulbs did indeed get hot. Since I don't use the plexiglass shield, the bulbs stay sufficiently cool without adding additional fans. The one fan creates enough noise so I don't want to add additional. I don't have any splashing or condensation on the bulbs or reflectors, so I'm happy with the way it is currently.
 

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Every option has pros/cons but I would base the decision on what you want to accomplish versus the risks. Acrylic is stronger, lighter, clearer... it is also much more likely to warp from the heat and adding fans adds alot of noise, it will scratch easily(tougher to clean), it is also more costly(will need replaced). I think thin glass would be clear enough, but you have to be careful not to break it and you might have to take a razor to it to keep up the clarity. You should be able to have either cut to size at the place of purchase so decide what factor is most important to you. I prefer no guard myself, if the fixture is elevated above the tank, just watch out for splashes.
 

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Plexiglass should be good enough. They do warp but depends on what thickness you are using. I have used 1/8" plexiglass cover for my LED fixture and it holds good, but not necessary that is works the same for T5HO.

However I did have coralife T5HO fixture before that had very thin plexi cover and never had any issues.
 
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