My plants grow too tall by using LED light and green spotted algae to start to grow. My old led light which is 20 watts did not promote any growth except for anubias and for water lettuce so I switched to 50 watts now... boom, my tank is a aquatic jungle.
I never used any MH or PC because I barely know these two kinds of lighting hahaha.
Just Did my 1st aquarium with dual Current USA LED.... not sure what to expect... last planted tank was with a coralife.... so yeah..... guess we will see..... I can say this, better know an electrician... LIKE F__K, Took me a day to wire it
As I understand it, metal halides are more a thing of the past. I've read certain companies, like IceCap, that made them lost so many sales that they had a serious financial trouble. These lights run hot and use a lot of electricity, but people used them because they produced a lot of light. But now, LED lights can produce as much light...just much more efficiently. And, most planted tanks don't need near that much light.
I think power compact fluorescent lights are essentially just folded high output T5s. From what I understand, fluorescents lights are more efficient than metal halides, but LEDs still have them beat. For a while, plant growers still used fluorescent lighting, because the color options were still better. But now, LED lights have just as good, if not better, color options. Also, LEDs last much longer. One has to regularly change bulbs in a fluorescent lighting system.
So, I believe there's really no contest. LEDs potentially have the power of metal halides and the color options of fluorescents while using much less electricity and lasting much longer than either. Furthermore, many LED systems offer adjustable light intensity and color to tailor them to a specific set up.
Once I got my first LED lighting system, more than 5 years ago now, I've never looked back.