Why red LEDs ?

[Reef Head]

Hey all, I'm new here. Thanks for all the advances you have made for the love of our hobby and the animals we love to keep. Please don't all frag me but I have a question, maybe I have missed it somewhere along the line. I've been researching this algae scrubber thing for quite sometime now on various related sites as a guest and still have not found out why you use the red LEDs?

[Peter]

Algae grows best when illuminated by light in warm color spectrum. There is no "warmer" spectrum than red LED lights. :)

[Floyd R Turbo]

Spectrum: photosynthesis happens predominantly in the deep red and somewhat in the blue-violet spectrum. Google "chlorophyll spectrum"

With fluorescent sources, "warm white" provides the best quantity of this bandwidth. LEDs are different - element specific vs phosphor specific, so you need to choose one that zeros in on the bandwidth, in this case, 660nm Deep Red

[Reef Head]

What would the blue spectrum be?

[Floyd R Turbo]

440-450nm royal blue LEDs usually hit both A&B spectra

[Reef Head]

Great thanks gents! I'm on the tail end of a 150g build that I've been working on for 2 1/2yrs now. It will be quite the system when complete. To date I haven't seen quite anything like it. I have spent literally thousands of hours researching, designing and constructing everything from cabinetry, electrical work, acrylic/polycarbonate work, lighting, filtration, sump design, plumbing and now on to algae scrubbers.

That being said, here is another question...for SM or maybe Floyd or anyone else that can provide me with a rational explanation. I noticed that in the earlier generations of SM's scrubbers as well as others on line from around the world, the ones that were constructed out of acrylic were usually black...why not use mirrored acrylic (aside from cost)? Why not make the most out of the light being emitted? Black absorbs light. I even noticed or it appeared that the lid to the new SURF2 had a black background. Baby bird here...

Thanks again Floyd for feeding me the red/blue LED info earlier.

[SantaMonica]

The mirror on the acrylic will not last too long; it's just a coating. Plus light will escape everywhere.

[Reef Head]

How/why would it escape?

[SantaMonica]

The ends of mirror acrylic are not coated.

[Floyd R Turbo]

One might use white acrylic, and I've seen that done, but even 1/4" opaque white will show light. The box would glow. Black blocks all light.

[Reef Head]

I'm thinking about a double layer... .125" mirror adhered to .125" black, then rabbet the back pannel, side and top of pannels capped with .125" x .25" black strip.
1. that would prevent the mirror from flaking over time
2. eliminate light bleed out on the ends/top
What do ya think?

[Floyd R Turbo]

The majority of the intensity comes from direct exposure from the LEDs. IMO, the most you're going to get is a few % boost in growth, which you can get just as easily by varying the flow, photoperiod, etc. But, you might be able to get away with a couple fewer LEDs. Seems like a lot of work. Just my 2c.

[Reef Head]

I agree. It would be alot of work, but it goes along with the rest of this system. I'm not trying to mass produce...just a one time design/build. If I get a few %...heck even a couple % in growth, it'll be worth it in the long run. I've been guilty of taking everything to the extreme and making things the absolute best they can be. I believe in doing everything 100% and then some! I like to keep afterthoughts and hindsight to a minimum. This is the biggest reason my 150g build has taken 2 1/2yrs and $8K+ just to get to where I'm at now.

[Floyd R Turbo]

That is true, being 100% satisfied with your creation is important. Let us know how it goes! I would be interested in how you bond the mirrored side of the acrylic to the black, I would think that solvent would not work, perhaps contact cement (loc-tite). Maybe bonding a couple large pieces together, then cutting them as one, etc. Sounds like a new topic

[Reef Head]

That was my thought. Just like bonding/gluing wood. Make the pieces larger than needed, then trim to size; table saw, edge routing and rabbeting etc...
Here is my thought: For bonding the mirror to black I was thinking that Aqueon (Dow Corning) Premium Aquarium Silicone would be applicable

1. Peel one side of protective paper from black sheet and evenly lay some zig-zag beads, just enough to create maybe a .5mm or less layer with minimal squeeze out after spreading/gluing/clamping (spread silicon on black to prevent scratching mirror coating from mirror piece while spreading with knife)

2. Use a wide mudder's/drywaller's knife/spatula 12" or larger width for even spreading, get the silicone spread as thin and even as possible (though using a knife larger than 12" may make it difficult to spread a thin layer considering the viscosity of silicone conversely using a narrower knife may make it difficult to spread the silicone even and uniformly)

3. Peel paper from mirror coating side of mirror sheet and place face (clear side) down on flat sturdy surface (protective paper still on clear side to prevent scratching later on when cutting/trimming), start the bond with the black sheet in hand and the mirror sheet on the surface, line up edges the best you can, begin by slightly bowing the black sheet at contact edge, slowly roll down black sheet to prevent bubble trapping ensuring even symmetrical contact

4. Using 2 pieces of thick plywood slightly larger than the acrylic (perimeter) that was bonded and at least 3/4" thick, sandwich acrylic, use a few boards of 2" x 4" stock (like 6 or more overall length of acrylic depending) a few inches longer than the plywood allowing for clamping, run perpendicular to grain of plywood evenly spaced and again sandwiching the plywood, then clamp the 2" x 4"s, allow for adequate cure time

[greenmachine]

A mirror does not reflect as much light as you may think. the light has to pass through the glass/acrylic where some % is absorbed ,then it hits the metal coating where it is scattered and re-directed out back through the glass where more is absorbed. this is why a "reflector" is better than a mirror.

[Pny]

Why do you want to use silicone to glue acrylic? (It will not stick to acrylic) instead of acrylic glue that the rest of us use? Does the acrylic glue not stick to the reflective surface?

[Reef Head]

I'm not sure if acrylic glue will react adversly to the mirror coating...for one acrylic glue actually melts the acrylic creating a weld (correct me if I'm wrong) if there is a layer of mirror flim I'm not sure it would even create the bond, at the price of mirrored acrylic I don't want to burn a piece to figure it out. Besides it is a large surface area I need to cover in addition Weld-on would evaporate before I could get the entire surface covered.

[Reef Head]

A mirror does not reflect as much light as you may think. the light has to pass through the glass/acrylic where some % is absorbed ,then it hits the metal coating where it is scattered and re-directed out back through the glass where more is absorbed. this is why a "reflector" is better than a mirror.

I get that part however, I don't want to build a scrubber with a 'reflector' that has direct exposure to the salt water. Salt water does not do nice things to aluminum. Even if it is washed on a daily basis. I speak from experience on that one, I work in/on the water (gulf) daily.