Glass Canopy vs. Plastic

[1fish2fish]

We have a 46 bow front Oceanic Sys tank it currently has the plastic canopy. I am worried about the large open area in the back and am wondering if the glass top wouldn't be better. Can anyone tell me how much light would be lost for the plants by using this type of canopy??

Thanks!
Angie

 

[Leopardess]

well, I'm not sure why you are worried about the space on the back...do you have something you are worried about it escaping?

Also, my glass hood does not fit the whole tank...it has plastic peices that slide onto the back part of the glass to allow you to account for filter intakes, heaters, cords, tubes, etc.

I'm not sure about losing light from this...glass is clearer, though I imagine they are almost the same.

 

[revfred]

I would stick with glass and take Leopardess' advice about the space on the back. The refractive index of plastic is higher than glass and increases with the thickness of the plastic. It COULD make a difference depending on a number of factors re: wattage, tank depth, plant needs, etc.

 

[1fish2fish]

I guess I need to explain a bit more. The canopy that came with the tank is black plastic, the back of it had places that were preforated you broke those pieces off to run your plumbing out of/into the tank. Then there is a space with two strips of glass where the light sits, then the black plastic lid to access the tank. The other canopy that you can get is all glass in the front and center, then the back is plastic (clear) that you cut the holes in yourself. That would lead to smaller holes and less chance of escape. I know it sounds nuts but I have had catfish jump out of tanks before, and my mom's large pleco got out and died. My pleco is at 8" long and when she is at the top of the tank you can touch her nose through the large hole in the back right now, I sat a flat rock over the hole just in case.

Anyway, we were looking at the glass canopy and the guy at the store told us that more light would be reflected out and I wondered how that would effect the light in the tank and for the plants. The only plants I have are java moss, java fern and some anubias.

Thanks
Angie

 

[Leopardess]

okay, I know exactly what you are talking about. are you just going to set your lights on top of the new glass hood? Because the front half is glass too and you could fit another strip of lights on top of it I highly doubt that you will lose any noticeable amount of light using glass. That is what most are made of. If you have the money, and want to cut down on the opening in the back, you might as well just get the glass one..they are better quality anyway, imo

 

[1fish2fish]

Thanks Leopardess. I don't want run away fish, but didn't want to sacrifice plant light either!

Thanks again!
Angie

 

[N©KI]

Apparently glass tops reduce effectiveness of Fluorescent lights up to 75%.
Is that true?

 

[Abercrombie6202]

okay, i just want to say something too, on my 75 gallon i have a glass top, but on my 20 high i have the plastic top, there both great too me, i do prefer the plastic sometimes more than the glass and the glass more than the plastic, with the glass you can fit more lighting on, view fish from the top without opening the tank and have a very heavy top, plus theres not as many holes that fish can climb out of. The plastic fits usually better on a tank and it does seem like light wouldn't be lost. But from what i've learned in Science black absorbs all light colors and most plastic tops are black. and white light has all colors in it so a lot of light that reflects off the water would be absorbed into the plastic part, i think. With glass light does shine through because it is transparent, but not all the light goes through, some light will be reflected back. that's my infrence, but who knows, i could be wrong

 

[revfred]

Go with the glass top ... it does not reduce the effectiveness of your fluorescent lighting 75%. There is . . . with any material . . . some light that escapes, but that is negligible, especially with glass. Look at it this way . . . if other materials were better than glass for tank tops, the manufacturers would be using IT, instead of glass. You definitely will lose more light with the plastic then with the glass . . . both in direct light that passes through the plastic and the reflected light off the plastic.

The LFS guy is both right and mistaken . . . yes . . . .but so little your plants won't notice ..... light is lost through a glass top. But the other hand, I wouldn't put a light over open water. It's dangerous, plus end caps, and the bulb pins eventually corrode. If there is a reflector, it gets a lot of crud on it, reducing it's effectiveness. Strictly speaking, having a good reflector is more important than whether you have a glass top. Get the glass top . . .

Good luck.

 

[N©KI]

I just did a little search on glass top effectiveness ( http://www.thekrib.com/Lights/lights-wozniak.html ) in reducing light, and your right Fred. It doesn't reduce it enough to matter.
I'm not sure where I heard that info ( I think it was the marine guy at the LFS )

Finally I can put that little nagging question to rest.

::Edit:: The link above is also a great resource for information about flourescent reflectors for your canopy.