To Good To be True -ES Cree 60W Pro LED Strip

Go to Rapidled.com and buy yourself 2 36 DIY led kits. Build it yourself. Cheaper and more dependable than somebody in China putting it together for $1 a day. I am getting ready to start a thread/build for my 125 gallon DIY LED build.

 

One AI sol will easily cover a 24x24 area, especially when mounted lengthways over the tank. I know some people on her who use one AI on a 24x24x24 cube with great results.

 

It's probably not cheaper when you calculate the time it takes to build but though I would say it's probably a higher quality item then something in china..Then again almost everything is built in china now-a-days.

I think I am going to save up and wait until early next year to purchase them...unless I get a heck of a deal

 

They have a mix of 70 and 40, I registered over 100 on the sand bed across the tank on my 6' with only 3 using an apogee meter. Your math doesn't show reality. I'm talking from real experience with actual lights and a meter on basically the exact tank the OP has. The fall off between lights is little of nothing. 4 is nice to have (it's what I use) but not necessary. I had plenty of spread with 3 and have to run my 4 at 60%.

I bought so many from the advice of posters that have no real experience with the lights. I actually would recommend swapping to all 40 degree optics and mounting at 14", you will get plenty of spread for a 24x24 and lots of punch to hit the sand bed. He can fill the tank with sps with that amount of lighting.

 

Agree with grimguy, if it only had 13" spread, I think we would all use PAR38s instead

 

D'oh, that's right, I was forgetting about the 70s.... Most people, IME, for SPS dominated tanks do recommend 1 per linear foot, I was thinking because they were 40 degree, but there are the 70s too... We tested one of our members AIs a while back and I remember we found this recommendation was definitely overkill, but not by that much actually, at least for a mature SPS dominated system. Remember while some people will say 100 PAR on the sandbed is good for SPS tanks, SPS still thrive at more like 300-400+ PAR. The 100 is based on the wider light cone of a halide, which is not the same with an LED. With an LED, if you have 100 PAR on the sand, the areas with 300+PAR will be patchier than with a MH due to the linearity of the light. The MH is more diffuse, the LED more directional. That may be fine though, it depends on the tank though.

Anyways, to fix my previous post and this time assume there is no drop off (which is unrealistic, but gives a best case scenario), the math is
TAN(Lens angle / 2) * distance * 2 (I used 1.5 in stead of 2 before, which provides a 75% reduction to account for drop off in PAR). So, at 14" above the tank, and not using the .75 factor, with the 70 degree lenses, you have:

Spread with 70 deg lenses
19" at the surface (15" with .75 factor)
36" 12" below surface (27" with .75 factor)
53" 24" below surface (40" with .75 factor)

So, with the 70s you do easily cover the tank. However, not with all your LEDs and the 70degree LEDs aren't penetrating deep.

For just the 40 deg lenses, again 14" from the surface, you get
10" at the surface (8" with .75 factor)
19" at 12" below surface (14" with .75 factor)
28" at 24" below surface (21" with .75 factor)

So, you cover your sandbed with 3, with just the 40 degree lenses, but you'd have a significant spotlight effect with just 40s. There would be significant gaps with virtually no direct light (other than reflected and scattered light), in between the lights at the upper parts of the tank especially. So, that makes sense to use 40s and 70s. The 40s punch down and the 70s provide even PAR in the upper parts of the tank and try to avoid some of the spotlighting. The high PAR areas are still sort of a weighted average of the two though, although the weighting will vary by depth.

We can see this from Sanjay's testing, which shows the actual PAR contour plots at 24 and 30".

from: Feature Article: LED Lighting Tests: Aquaillumination, Blue Moon, Eco-Lamp KR-91, Ecoxotic Panorama — Advanced Aquarist's Online Magazine

From it, we can see that at 24" we are getting PAR of 80-100 for a 24" area, however, that drops of substantially. For SPS, as mentioned, to thrive, and get best color and growth, we typically want 300+ PAR. If you look at that area, you’re only at a 6" radius at 24". Sanjay doesn't provide numbers for other areas of the tank, but the light cones however, will more or less follow the formula I provided. What you can get away with depends what you want to keep and where. For a mature SPS dominated tank, packed to the brim with SPS, the 1 per linear foot makes more sense. For a more sparsely stocked tank, I agree, the 70deg lenses mixed in, will allow you to get away with less.