Hi everybody,
As i am looking into building my own LED system for my reef tank in progress, i have been looking at a lot of stuff for them.

First of all, the reason why the chinese company puts 800 led's onto one of their fixtures is because each of those led's are not intense enough to supply a good amount of light. 800 led's seems to be a waste for such an endevour. LED companies have recently been making 1, 3, and 5 watt (some even go up to 12 watts each but are very pricey right now) LED's which have a much more reasonable light output.

Some forum's i've seen have people using about 24 LED's for a 29 gallon reef tank have noticed improvements in their corals using 3 watt led's. This is for a reef tank which seems to require about two to three times as much light as a planted tank and 4-5 times as much for an unplanted tank. So taking the 24 three watt LED's used for a 29 gallon tank and extrapolating for a planted 29 gallon tank, you should only need about 12 LED's. Cut that in half yet again for a fish-only tank. Most people i've seen using these for their reefs use a mixture of 5000-10000 K LED's and 420-450nm blue LED's. For a planted tank, this should be complimentary.

The Kelvin rating for the white led's, btw, is controlled by the (i believe) amperage (500 mA - 1000 mA) so is adjustable by the user.

The other idea that LED's have a better spectral output is quite true with a few misconceptions. The posted images of the chlorophill spectral sensitivites are quite correct. The WHITE LED's have a spectral response closely matching the chlorophill sensitivities as well as having a response in much of the region it is not sensitive to. The blue led's (actinic as you have heard) have only an output between approximately 410-500nm which is perfect for plants and corals.

The terms you have heard as wattage isnt the light output of the lamps, but the energy usage. Since LED's are quite a bit more efficiant than fluorescent lamps, the wattage you see relative to the output is skewed in comparison. Also, the light coming from a fluorescent light fixture is being output over a much wider area than the LED's so the lumen output you get from something like a T5 bulb isnt being directed fully downward into a tank, unlike the LED which has a very tight light output. So, you get all the energy focused where it belongs which also leads to you needing less wattage and light output. But, you may have to raise the fixture over the tank to get the spread you need and may also have to add a few LED's to help with the brightness after being raised.

I'm planning on using 24 three watt LED's for my 20 gallon reef tank, 12 white and 12 blue. I have priced the cost of these and the power supply required and its a reasonbly priced 150 bucks to build it yourself without purchasing a kit. You'll need to get a heat sink so that will add to the cost. I'm using the heat sink from an old stereo amplifier so that was pretty much no cost (at this time but was when i purchased it several years ago) for me. I may find that i will have to add another set of LED's onto the fixture but when you DIY, its a lot easier to modify your system.

If everyone would like, when i build my system, i'll do a step by step with everything involved as well as keep track of the growth of the corals i add to the tank. Then I'll be able to better inform you about how many LED's you'll have to use for your tanks. Personally, if it works out, 150 bucks for a system that will work for 5 years with no replacement is well worth the cost.

More research has come up with some great numbers. I've found that Cree XP-G white LED's can output as much as 493 Lumens per LED if driven at 1.5 amps. But thats a lot of amps. If you bump it back down to 1 amp, you can still get 347 lumens from a single LED. So driving 12 of these at 1 amp, you can get 4164 lumens! They are quite well priced at around 7 bucks. A royal blue Cree XP-E can output 72 lumens per watt and if driven at 3 watts (1amp) you can obtain 216 lumens per LED. Drive 12 of those and you have 2592 lumens and are only about 5 bucks per LED. So combine these two for your system and you can have a total of 6756 lumens for 144 bucks minus the driver which is about 58 dollars plus shipping. This provides 6756 lumens at only 72 watts of power.

Compare this to the T5HO 54 watt which outputs 5000 lumens but is not as effective due to the PAR/PUR output and light dispursion. Lets say that due to directional decreases in the T5HO and par rating decrease the effectiveness of the bulb, assuming 180 degrees of the light is not falling directly into the water and a 10% better PAR from the LED this give us an effective 2000 lumens from the T5HO reaching the water. Which means you would need 3 of them to match the effectiveness of the LED's. I'm assuming this on a conservative loss. This also brings up power usage to 162 watts which is twice the power usage as the LEDs. This is only an estimate though but even with a reflector on the T5 housing which is usually only about a 60% reflectivity, the LED's are still much more efficiant. Add that to the continuing cost for replace bulbs every 6-9 months compared to the LED's 17,000 hrs (at about 1amp instead of 350mA, it is decreased from 50000 to 17,000) and is still almost 4 years without replacement if assuming you keep your lights on 12 hrs a day 365 days a year.

If you get an amperage adjustable driver, you can change the kelvin rating anywhere from 5000 - 10000K (which also changes the lumen output). This can be quite useful when you'd like to adjust for realistic enviroments.

If you're not doing a reef, you can supplement the royal blue (actinic) LEDs with the white and gain up to 8328 lumens for 24 LEDs at 1 amp. That should be quite sufficiant for many planted aquariums and there is definately room (considering they're only 3.5-4mm each) for expansion.

I'll keep you updated when i get more information so we can all learn something.

check out rapidled.com. has awesome cree lighting etc