which color plexiglass for backdrop light transmission?

[RyanBrucks]

Hey reefers,

I'd like to adhere a piece of translucent blue plexiglass to the back of my tank, and then use some sort of dimmable LEDs to add backlighting.

I want to go for the 'deep blue' look, with a gradient to a lighter blue near the top.

Here is a real life example of this:


The in-tank lighting should help(3x 350 MH
2x 160 VHO), but I'm not sure how bright the various plastics will look with the amount of lighting in the tank, or how much backlighting is needed to make it worthwhile.

Here is what seems to be the standard plexiglass color chart

I'm thinking of using Blue 2051 Translucent, because of its deep color. I fear that one of the ligher blue plexiglass colors (Blue 2648) might keep their brightness to the depths of my 30" tank, but this may not be the case. Can anybody tell me how these plastics look in a tank with lighting?

I don't think I have enough room for fluorescents, so I'm going to try and use LEDs. Is there anybody out there with a good knowledge of LEDs?

Ryan

[Justjoe]

Most public aquariums that do this type of back drop (especially for jellies) use a translucent blue and a piece of translucent white for a more even spread of the light. It may be tough to get the look you are going for if you don't have room behind the tank.
Home Depot type stores now have a variety of LED fixtures available.

[gatohoser]

Not that plexiglass is any less good of an idea but in the Monterey Bay aquarium they use sheets of thin blue plastic. Just did a search for transparent blue plastic sheet and found this on ebay. Just an interesting thing. http://cgi.ebay.com/ebaymotors/Trans...temZ8053032627

[Crazy4salth2o]

What a great idea. I might try that. But it seems as though the LED or platic would not difuse enough light since it is so concentrated at a point. Let us know how this progresses.

[RyanBrucks]

i'll definitely post back when i get the ball rolling on this.

i've been reading up on LEDs, and from what I can gather its difficult to estimate how bright an LED is going to be.

I found this page helpful

The best I can seem to find are 18000 MCD with a 30degree beam angle.

But according to that site:
"By way of comparison, a typical 100 watt incandescent bulb puts out around 1700 lumen - if that light is radiated equally in all directions, it will have a brightness of around 135,000 mcd. Focused into a 20° beam, it will have a brightness of around 18,000,000 mcd"

According to a lumen calculator on that site, an LED with 18000 MCD and a 30 degree beam only puts out about 4 lumens.

I wonder if this means I would literally need hundreds of such LEDs to get the effect I am going for?

[RyanBrucks]

Ok, I ordered some acrylic, blue traslucent 2051 1/8". Also got some white translucent, that i MIGHT use on the back wall behind the tank to diffuse more light (or could not use it, and the high-contrast spongey blue wall paint might make my tank look almost like a painting, could be neat have to see it first).

Also got 2 of these LED lightboards:

LuxStrip 1W LED Light Engine

270 lumens, and I will have 2 of these. hoping it looks nice and bright. I might mount it at a slight angle towards the tank to get the hotspot look I am going for, but I think it will work.

It's dimmable 0-100%, so naturally I want to put it on a timer and have it coincide with the actinics, to try and blend in their popping, which I think would be really nice.

It requires a 5k ohm potentiometer to dim.

Has anybody heard of a way to put a potentiometer on a timer? Or is this question so obscure that it deserves its own thread? Or is it really obvious and im late for the game as usual?

Thanks!
Ryan

[RyanBrucks]

I'm going to go just 1 step further with this.

I decided I am going to use the blue and white acrylic to construct a box about 1.25" wide. Near the top of this box I will use very thin 1/16" clear acrylic to make basically, a super long thin aquarium. It will have about 0.25" of water, and will be a very slight incline. I will also tack some scrap acrylic to the bottom of this 'mini tank' at random places to create water turbulence instead of a smooth sheet.

I will use a tiny pump (and minisump to maintain waterlevels) to run water from the low end back to the high end. the pump can probably be some small airlift pump, and minisump can probably just be a plastic soda bottle.

Whats the purpose of this you ask?
the water cascading down the slope and over the scrap acrylic should have some turbulence to it, and will make the backlight have some kind of lightray effect on it. I'll prototype this to make sure the multiple LEDs dont diffuse the effect too much before actually constructing it, but I think if I can get the water to have some surface turbulence that it will look sweet.

Should get the stuff I ordered in about two weeks. I hate waiting because then I keep finding ways to make the project more complicated!

[RyanBrucks]

Finally got the translucent acrylic sheets today and built a quick frame for it out of 2x2s. It has 12 LED lights mounted above.



You can see me in the reflection a bit. In the end it will be mostly rockwork and coral being reflected.



This shows the hotspots near the LEDs. The camera isn't picking that up right, its so bright that its started some kind of banding artifact. The color transitions are much smoother in real life, and the top ~4" of the blue acrylic is going to be covered by the tank hood, so it should be a pretty smooth gradient.

This shot blocking out the very top gives the camera an easier job of things:



Right now its just a sheet of 1/8" white acrylic on the back, but I think I might try adding some reflective material up top to make the bright spot a smoother gradient down the height. Overall I'm pretty happy with the look but still looking to experiment with it, since I have ~1.5months before I actually get my tank

Did some testing and the water-flowing trick is pretty cool (resembles lightbeams in a turbulent ocean). I found some computer RAM water cooling blocks that fit my LED board perfectly so I'm going to try something soon. I need to order some thinner clear acrylic though, as my scrap 3/8" acrlic is way too thick and the edges would block too much light.

Cheers,
Ryan

[m2434]

Looks great. I think you've inspired me!

[H20ENG]

One thought-
If you angled your halides back toward the wall slightly, and painted the wall a bright white behind the tank, wouldnt it do the same thing, using light spill from the halides?

[RyanBrucks]

I guess I'll find out when i actually get my tank

In theory I could, but I wouldn't be able to do any custom timing of the backlight that would operate on a different schedule than MH. Also, MH is not dimmable, and a controlled dimmable backlight is what I am trying to achieve.

But also I wouldn't really want to angle my MHs away from the tank much, and I'm not sure if the same 'hotspot' would work out. I'll try it and let you know I have some pure white scrap acrylic I could use (currently its on the backside of my lightbox, theres 1.5" between blue and white).

[chrismunn]

thats pretty rad

[MMM33732]

awesome idea. i'm deff gunna look into this. the plastic on ebay seems like it would be too transparent in my opinion. is that what you ended up going with or did you get the plexi? i'm curious as to how this would look on a 6ft tank. i'm wondering if it would look better with a smaller section of led say 12inches or so to simulate the sun in one spot or if a longer section of leds, like 4-5ft., would be better since it would be more even throughout the length of the tank...

[RyanBrucks]

I used blue translucent 2051 acrylic, 1/8" thick. All acrylic manufactures seem to use the same colorsheet which helps. On the back of the lightbox is plain white acrylic that helps diffuse the light some (least i think so).

As another tip, I saw a really tiny Lights of America fluorescent fixture at wall mart. It's 24watts, and about 1 inch thick including the bulb/fixture, and the cord comes out on the side.

It costs $10 dollars so I picked it up (can always find a use for something that handy) and looks about 80-90% as bright as the LEDs I paid so much for :P Obviously you won't be able to dim the fluorescent, but its a MUCH cheaper and easier to setup alternative that provides rougly the same results. It's about 23" long so I wouldn't be able to fit 2 of them, but for a 6 foot tank you could easily (my tank is 6feet also, but i have vertical overflows so I only made the lightbox big enough to fill the gap, ~48", ~45" usable space between the frame).

"i'm wondering if it would look better with a smaller section of led say 12inches or so to simulate the sun in one spot or if a longer section of leds, like 4-5ft."


I'd say thats purely an artistic choice. Also, the deeper down in the water, the more evenly diffused the light would appear. Also consider the layout of your aquascaping and how muck background you will see. I think the visual effect in the photo I posted in the first post of this thread is really cool, but it mostly works because of the 'canyon' aquascaping.

[JCTewks]

where are the pics? only red X's for me

[RyanBrucks]

hmmm *** they dissapeared for me too. when i try to visit the RC photo gallery, it says not found.

not sure if its related, but as of a day or so ago, RC no longer seems to work correclty in firefox for me. Half of the images are gone (including avatars and reply buttons), and the RC logo isnt even there.

I'm so switching back to IE

[chrissreef]

Please post pics when the halides are on. I think the halides will make the front too bright and it won't work... but I could be wrong! if so, I want some!

[RyanBrucks]

well if the MHs do overpowe during the day I won't be too upset, the backlight will still help to even out any shadows from the rockwork that might ruin the illusion.

but IMO the real coolness will be at night time. I just watched a show called 'blue planet' last night, and they did lots of dusk shots. it was surprising how bright blue the ocean still looked even though the reef can still be pretty dark. I hope to kind of get that effect at night.

[chrissreef]

I agree for the night look =) Add a few LED's in the canopy too so you get a blue spakle over the reef.

pm me when it's all set up =) I'm thinkin gabout putting a mirror on the back so it looks like I have 2x the corals/fish that I really have. It's looked great in the past but I'm up for trying something new and switching back if it doesn'twork. ok, ttyl!

[mysterybox]

I had a nice piece of deep blue transparent plexiglass, with a nice T-5 light. It looked really cool until, .....uh....until...calc algae took over! Oh, well!