PAR readings!
Here's a new article on reef lighting...
http://www.advancedaquarist.com/2012/10/aafeature
"Our main conclusion from the above is that violet and blue light are most important for marine photosynthetic organisms."
Keep in mind, this conclusion is being applied to all corals collectively, and is not a focus on aquarium species that are grown in 6' deep water.
@lasse would you recommend getting the dream chip for my 8' 30" 30"
I don't remember what the spectral plot of the dreamchip was, but it pretty much follows this. I don't remember if it had much in the 470-500 range, and I don't remember if it had a small 660nm peak. Those are the only areas I don't think it covers, otherwise the concept of it is solid.
You are using a constant voltage driver. Normally - it is not recommended to use this because of that the relationship between the voltage and the amperage is not linear with a LED. A very small change of the voltage cause a rather high change of the current. 2100 mA to this chip is also a little to much. It is recommended to use a constant current source instead - when if you choose 2000 mA - the driver will never exceed that number - it will adjust the voltage instead.
Sincerely Lasse
This info should be applied to all led builds. Focus most of the build on 400-480nm, and add 500nm-660nm for visual appeal in small amounts, either through the white leds, or separate colored leds. After I tested both warmer leds and separate colored leds on my fixtures, the ones that focus specifically on 480-520 and 660nm tend to look better visually overall when used in small amounts compared to using just warmer whites, or not using these wavelengths at all. 470nm, 490nm, and 660nm actually look white when placed close together.
I don't remember what the spectral plot of the dreamchip was, but it pretty much follows this. I don't remember if it had much in the 470-500 range, and I don't remember if it had a small 660nm peak. Those are the only areas I don't think it covers, otherwise the concept of it is solid.
The reason why taking with 16 000 K was to cover the gap 460-490 nm and the 10 000 K was to get some red. Today there is a redish phosphorus available so probably it will come more red in the future.
Sincerely Lasse
when diving I remember LOTS of corals lower than 6-8' deep, if they were all that shallow who needs scuba gear!
free divers go much lower than 8' I have zero experience and I snorkeled that deep to see corals
You are using a constant voltage driver. Normally - it is not recommended to use this because of that the relationship between the voltage and the amperage is not linear with a LED. A very small change of the voltage cause a rather high change of the current. 2100 mA to this chip is also a little to much. It is recommended to use a constant current source instead - when if you choose 2000 mA - the driver will never exceed that number - it will adjust the voltage instead.
Sincerely Lasse
I have done a lot of tests i different areas in my aquarium with one glass window (120*65*60 cm). The same results everywhere. We are talking about a distance of 60 cm in water and a concentration of the lighting area with around 40 % through the differences of the refractive index between air and water. I do not think you loss 40 % of the intensity in 60 cm of water. There is other people I know that have the same experiences when working with lenses and water depths around 60 cm. And I´m using lenses - not reflectors. For reflectors - I do not know the result - I have not test. I was myself surprised over the result with my calculations of difference of the beam area in water vs air, so if you find any major mistake in my calculations you are welcome to correct me.
I found 44 % lesser area - it means for me somewhere between 30 - 45 % in reality because my formulas is based on a average of the refractive index and a calm surface. It is also important to stress that I use ozone in this aquarium so I do not have the normal amount of yellow humus in my water. My water is very clear, some particle but not colored water
I know that reflection can have a huge importance on PAR readings, I have seen examples with bare glass aquariums how you can changes the PAR readings just through not paint your backside of the aquarium or to chose a colored film as a background. This is not the case with my aquarium. The whole backside is covered by artificial rocks
However - I´ll do some experience later on when my Dream Chips are up and running - and I´ll try to find a way to do the measurements without any chance of reflection.
Sincerely Lasse
I used a laptop power supply with a home-made driver to get the exact power needed, no dimmer. However, you can get many ready-made drivers for the 20W on Fleabay for a reasonable price. The chip draws almost 2.1A at 12V.
On my 7g I was using only the 20W hybrid LED and it's the best light I've had up to now, if looking at coral growth. On your 12g you might want to go for a slightly larger LED or add another 10W Blue/RoyalBlue chip, but I would say only if you're having SPS corals.
Lasse i appreciate a lot all your help but i have not been able to find the driver you are telling me i dont know if you have any website. Can you tell me what can happen if i would use the same driver which acabgd is telling me. Thankss
This driver ELN-60-27 (P or D) you can find at www.rapidled.com With these drivers you can run 2 pcs of AC-RC type 20 watts chip in a daisy chain (no more or less) Adjust the current to 2000 mA. I think you should have at least 2 over your tank.
The ELN-30 - 15 (D or P) you can find at http://www.powergatellc.com/.
It manage 1 pcs of 20 watts of AC-RC type
Sincerely Lasse