New LED lights

[Second Hand Pat]

architect1, here's another tank lit by the 70W MH recommended by Darrell.

[ericatdallas]

Did anyone ask what kind of plants the OP is growing... I think that matters and more is not necessarily better and didn't see it when I browsed through.

I can really only speak on LEDs b/c I am terrible at when it comes to aquatic plants. The reason LEDs are theoreticlly better for growing is that they can be 'tuned' to target specific wavelengths that plants use for photosynthesis. Some anecdotal evidence points that even using a tuned LED may not be sufficient for optimal plant growth. They are also considered efficient b/c less heat is given off for them to emit visible light.

I can only speculate on four possible reasons:
1) The LED the person is using is NOT tuned to the specific chlorophyll type that he thinks the plant has
2) The LED specifications are a 'lie' or some other real world reason. For instance, changing the voltage of the LED can shift the wavelength bringing it out of the optimal range. Also, overheated and overdriven LEDs will emit shorter wavelengths.
3) Plants evolved to absorb the full spectrum and not just the one or two 'peak' wavelengths.
4) LEDs are so effective and providing light to plants, they are unable to compensate with available nutrients and/or are signaled to protect themself b/c they are evolved to react to times of drought or high heat. An example of this is with mosses. They evolved in low-light and moist environments so they have certain mechanisms in place to protect them in the short-term (including changing their chlorophyll content) to compensate. That change may be totaly healthy but may look like the plant is dying. Think autumn and leaf color changes....

Also, if the Kelvin rating is being used correctly, a 10,000K bulb -should- provide what the plant needs but a lot of it will be shifted in the wrong wavelengths and it will consume energy it output that is not used for photosynthesis. So a 40W 10K bulb will provide some of the light the plant needs, but maybe not in sufficient quantity for optimal growth while a 10W LED light may provide the wrong wavelength and be ineffecitve and a two 3W bulbs may provide everything the plant needs. Further, algae use this light very efficiently. It outputs in the blue spectrum very efficiently.

Not trying to overcomplicate things, but I think it goes back to "what type of plants". Most of what is said correct and are probably good guidelines to follow (especially what ghulag wrote). But I wanted to point out some of the misconceptions I've read about LEDs in other places as many people don't know about the wavelength shift of overdriven and overheated LEDs.

[Darrell Ward]

What it comes down to in the end is balance. You have to balance light with nutrients, not as easy as it sounds. To make it easy on myself, and also to make the tank as discus friendly as possible (easy to keep clean), I only use plants that do not require substrate for the roots. That means that I can tie them to driftwood, or throw them in the tank to float. They pull all the macros they need directly from the water itself, which also benifits water quality. In this way, all I have to add is micro elements, a little Seachem Flourish once a week or so takes care of this. Much, much easier than trying to balance CO2, fertz, and all that other BS with your lighting.