Cgy_Betta_Guy Posted November 23, 2012 Report Share Posted November 23, 2012 (edited) I have decided to do away with my stock canopy and upgrade my lighting on my planted tanks and i will be getting glass lids made. My lighting will be a 2x54w t5ho. I need lids in winter because its so dry here that i am having to top up my tank every couple days as i am losing water at a rate of about a gallon a day. The lid will be made of 2 pieces and will not be hinged so the 2 will basically butt up against each other supported on the ends. My question is what glass thickness would be suitable for a length spanning 47 inches x 6 inches wide the other will be. 47 x 9.25 inches. Should i go with 5mm glass and will that affect the light getting through the glass? Would 4mm be sufficient and not sag in the middle? What do you think? Edited November 23, 2012 by Cgy_Betta_Guy Quote Link to comment Share on other sites More sharing options...
Rainbowric Posted November 23, 2012 Report Share Posted November 23, 2012 (edited) On my 36 " tanks ...4 mm is sufficient, little sag is noticed. Even one tank at 40 inches wide, however it is 22 inches deep. However on my 48 inch tanks there is a fare bit of sag. It is quite difficult to find 5 mm glass so I went to 6 mm. Then the problem comes in finding hindges that will work with that thickness. But it can be done. I have never found 5 mm glass. A far as light distortion ...there is none between 4 mm and 6 mm. I even did two 48 inch glass tops with 6mm starfire glass and no noticeable difference on light. Edited November 23, 2012 by Rainbowric Quote Link to comment Share on other sites More sharing options...
jvision Posted November 23, 2012 Report Share Posted November 23, 2012 Just make sure the bulbs are raised up off the glass. I've had glass tops crack from the heat put out by T5HO. A little air flow around the bulbs would be great as well. Quote Link to comment Share on other sites More sharing options...
cainechow Posted November 23, 2012 Report Share Posted November 23, 2012 (edited) I'm assuming you are supporting front and back along the long edges yes? With a max width of under 10" even 3mm glass won't really sag while it is sitting on the supports. On the other hand if you are supporting along the short edges, the 4mm glass will sag over that 4 foot length. Does the tank have center bracing or euro? If it is euro, I'd recommend doing two braces that sit on the euro bracing. so that you are supported in the middle so that your run isn't so long. Actually probably one brace in the middle. If you could find a way to put it in there w/o silicone that would be a neat trick. Edited November 23, 2012 by cainechow Quote Link to comment Share on other sites More sharing options...
Cgy_Betta_Guy Posted November 23, 2012 Author Report Share Posted November 23, 2012 Good to know that the light wont be visibly affected by the glass at these lower thicknesses. There is no bracing on the center of the tank and i dont plan on putting any on. I am getting plastic glass hangers that hook over the glass to support the lids but wont have them on the front viewable side which is the 6 inch piece if i can avoid it for esthetics. And i had planned on putting short blocks to raise light up off the glass. Quote Link to comment Share on other sites More sharing options...
Cgy_Betta_Guy Posted November 23, 2012 Author Report Share Posted November 23, 2012 (edited) Double post. Thanks for the opinions guys. Main concern is light transmission through the glass since its a planted tank. Edited November 23, 2012 by Cgy_Betta_Guy Quote Link to comment Share on other sites More sharing options...
Iceturf Posted November 23, 2012 Report Share Posted November 23, 2012 Most of the light loss will actually be from the index of refraction, which will not change based upon the thickness of the glass. Usually for most surfaces like glass, the light that makes it in often makes it out (no loss of energy unless the glass has scratches, why they do it for fibre optics, unique characteristics under 'average' conditions.) I would go for the thicker glass, limiting thickness only out of cost and weight. Your going to have similar 'back' reflection in either case and most glass applications don't loose noticeable amounts of light to slight pigmentation of the glass itself. Light literately 'weaves' between the glass molecules, its really neat. What you should be most worried about is if the type of glass you use blocks certain near UV rays that plants get a lot of energy out of (close to the 400nm range). From what I understand tempered glass and certain plexi glass materials block this waverange, but I'm not 100% sure about tempered. I still get sunburned by a tempered glass window. Quote Link to comment Share on other sites More sharing options...
Iceturf Posted November 23, 2012 Report Share Posted November 23, 2012 I wouldn't worry about it. The reason fish tanks 'work' is because the index of refraction between glass and water does not cause a large amount of refraction. Thus the light comes through without the same 'skew' that looking down at a pond has. Quote Link to comment Share on other sites More sharing options...
Iceturf Posted November 23, 2012 Report Share Posted November 23, 2012 Also, there is very little your can practically do about the 'back reflection'. Most coatings may make the surface more permeable towards a certain wavelength range, but are not something you or I could easily get ahold of. Source - I am an engineering student, first year we had to do a big thing on light. Not that I remember the exact formulas, but that is how it works. Quote Link to comment Share on other sites More sharing options...
Cgy_Betta_Guy Posted November 23, 2012 Author Report Share Posted November 23, 2012 great info. thanks. guess i will see what the glass guys say about sagging but will likely go with 5 or 6 mm if available. Quote Link to comment Share on other sites More sharing options...
Iceturf Posted November 23, 2012 Report Share Posted November 23, 2012 (edited) PS, don't go to crystal glass, I don't know where your going but most glass places like crystal glass charge a fortune for nothing Edited November 24, 2012 by Iceturf Quote Link to comment Share on other sites More sharing options...
Cgy_Betta_Guy Posted November 24, 2012 Author Report Share Posted November 24, 2012 probably going to chinook glass in calgary. Quote Link to comment Share on other sites More sharing options...
FishTankBoy Posted November 24, 2012 Report Share Posted November 24, 2012 You can try Dave at ConceptAquatics.com for the glass. Why not pick up an auto top off? Quote Link to comment Share on other sites More sharing options...
Cgy_Betta_Guy Posted November 25, 2012 Author Report Share Posted November 25, 2012 Auto top off isnt practical for me... would require me putting a bucket next to the tanks which is kinda ugly and takes up space. Quote Link to comment Share on other sites More sharing options...
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