Flourescent Light vs Metal Halide

[aquafrogstuff]

I was interested to hear from people who've tried or had experience with both flourescent and metal halide lighting. In particular I was interested to know which type of lighting people preferred for a planted discus tank?

[ILLUSN]

I've used bot with good results, on any tank beeper than 45-50cm flouros are useless, even CF's and T5's are at their limit by 50-55cm, you'll loose all the lower leaves on your stem plants and your swords and crypts and lillies will strat growing up towards the light, you'll deffinately notice it once your bulbs hit the 4mth old mark, T8's IME are only good for 6 mths, CF's (the 96w that i use) are good for around 9 and T5's 12 MAX.

Halides are fantasic for deep tanks, they'll grow glosso like a carpet and keep your tiger lotuses nice and low, dont be suprised if you emersed growth on your swords and wysteria if your using one. problem is these things are only goot for a MAx area of 2 square foot, so on my 4x2x2 I had to use 2 lamp, at 250w each they are expensive to run. also the spectrum of these tend to drift over time so you'll need to replace them annually, they get HOT, they provide a very bright spot in the tank directly under each globe which the discus didn't seem to mind swimming through, but none lingred there and a cone (terracotta pot) in the bright spot was always ignored.

[aquafrogstuff]

Great, thanks. I have set up a temporary arrangement with two 150W metal halides using 3,000k tubes. (You can see it here http://www.discusforums.com/forum/viewtopic.php?t=17200) I've since moved the fittings apart because they tended to encourage algae growth on the driftwood. Permanent fitting on its way. Tank is 28" deep (near 700mm) so looks like MH was the right answer.

Keen to hear more feedback from others also.

[aquafrogstuff]

I also meant to ask, in your opinion, what Kelvin rating do you find works best?

I see a lot of info on the net about 6,500k for fresh water aquariums. Is this right?

[ILLUSN]

kelvin rateing is not as important as spectrum, in the old days 6500k looked like daylight and so it was assumed it was daylight, in reality its just the spectrum that our eyes are most sensitive to.

look at any halide bulb with spectral info on the box, get one with peaks in the blue and red regions, if you cant find that go for something between 4500k and 6500k, that way your more likely to get good red spectral peaks which is the wavelength that green plants use. if your growing mostly red plants go for a bulb between 10000k and 6500k as red plants use blue light. any globe over 10000k is useless, any bulb below 3500k is useless.

[aquafrogstuff]

Great, thanks again.