I am planning a long term project. A big discus tank, and for that I have been researching into LED lighting systems. I have definitely ruled out commercially available modules because:
1. They are expensive and
2. I won't get the flexibility in lighting schemes that I can easily achieve by a DIY LED system.
Currently I have a marineland LED the I got the the 20 gallon, and I have a 10 gallon running on CFL (13 W). Hands down plants under the CFL are doing much better. But I know I will be able to get a combination of LEDs that will give me similar spectrum to a CFL or a fluorescent light. As mikaila mentioned earlier, Cree LEDs are good quality.
I found this link http://theaquaticgazette.com/2011/05...cus-biotope-2/
which describes a very elegant LED system. I dare not say it is DIY as you will need a significant electronics knowledge to build one yourself. A slightly expensive but cheaper than commercial LED systems option is to get modules. For any high power LED system, you need 3 modules.
1. A power supply
2. A constant current LED driver (some times 1 and 2 come as a single module)
3. LED modules. (some times 2 and 3 come as a single module)
All of these can be bought on http://www.digikey.com/
(I don't advertise for digikey, but they are the best place to find all the electronic components in the US.)
If you are careful enough in selecting the components, requirement of fans and heat sinks can be kept away from the aquarium. The heat is generated in the driver circuits and not the LED itself (compared to other lighting options).
Considering that LED lighting has found a stronghold in high light requiring markets like street lighting, architectural lighting, car headlights etc, I feel it is just a matter of picking up a ready made module that suits the requirements as an aquarium light and putting it to use.
I am really looking forward to build a circuit that will allow me to simulate sunrises, sunsets even cloudy days using LEDs.
PS: I am just an electircal engineer trying to relive my soldering days. :D