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Itwasntme 11-28-2012 06:25 AM

T8->leds, what explains the difference?
I changed my T8s (poor ballasts without reflectors) 4x58w (1xPhilips Aquarelle, 3xPhilips TLD 865) to 4x27w 6500K leds. 2000 lumen/light. Leds are Cree powerleds (wich ones???), 9 per light. Thats all I know about those leds, not these but near: They have been over the tank for a month. Growth and colours of plants has changed dramatically thoug I was very pleased even with T8s. Swords that were red last time when I had metalhalides are red again now. No algea anywhere. I havent done any changes to fertilizing, Excel dosing the same as earlier.

So, leds are pretty odd to me and Im wondering what explains the difference of better growth and still not having algaes? With T8s I had nearly 20 000 lumens, now only 8000. I know they are not compearable to each other but how come? Please enlight me!

micheljq 11-28-2012 02:02 PM

Hello, I cannot answer your question but the leds are pretty powerful, 27 watts. I would like to know more about them.


Steve001 11-28-2012 03:07 PM

Lumens aren't applicable because they refer to how bright a light looks to the human eye. What you need to look at is the photosynthetic active radiation (PAR) a source of light outputs. PAR is what matters to plants.

Itwasntme 11-30-2012 01:33 PM

micheljg: They are actually these but there is nothing special to know.

Steve001, do you think its PAR what makes the difference? Unfortunately I cant get PARmeter. Is it possible that leds have more PAR/PUR than T8s but still "less powerful" to grow algae?

blink 11-30-2012 07:52 PM

Could be due to lack of reflectors, 20000 lumens that is not getting into the tank is useless.

Itwasntme 12-01-2012 05:06 AM

Might be, but what explains that the sword is as red as with metalhalides but still no algae? When I used to have MH, I had to bump tons of C02 and fertz not getting algae farm, but now daily Excell seems to do the trick. Id like to understand better the quality of the light of leds.

kevmo911 12-01-2012 05:43 AM

Any possible difference in total PAR aside, it's very likely that the T8's versus LED's will make your plants look very different (color-wise), even if they have the same stated Kelvin rating.

I'm not knocking LED's, but keep in mind that all identical Kelvin ratings are not ...well, identical.

Itwasntme 12-02-2012 02:31 PM

3 Attachment(s)
Hmmm...I`m still curious. If Im correct, plants do protect themselves from too strong light by turning red, right? The sword was green-lightly brownishs for eight months (after giving MH away), now its growing strong rasberryred leaves. Protecting itsself against what now? The answer cant be kelvins.

Plants also show much more bush like growth than with T8s plus the distance between leaves (donno the right english word for this) has shorteded significantly.

I dont mean to argue, just keen on whats the difference.

1 pic: the sword hybrid I got from Mr. Falck personally, colours are different from reality
2 pic: L palustris is mainly orange (?)
3 pic: a bit overgrown...?

james1542 12-02-2012 04:16 PM

Yea think of the Kelvin rating as the average color of your light, but if you look at the spectrograph of 2 different 6500k lights, they could look totally different. Everything that you are describing about your plants indicates you have more light, more specifically more PAR hitting your plants.

To answer your algae question, think of how different the tank looks with LEDS vs florescent. With florescent light is thrown in every which way, as this is the nature of the bulb, you have all these bulbs draped over the tank, with half of it being shined into reflectors. When you look at the tank, everything is illuminated, there are no shadows, which means for the algae-which doesn't need much light to grow-tons of suitable habitat. And since your plants were not red, and the internodal distances were increasing(stretching for light) I'm guessing the plants weren't too pleased either. Now contrast this with LED's, where you have a point source of very bright light, all coming from one direction, not being wasted on reflectors and scatter. You get shadows, and you get really bright light on the leaves, where it counts the most. The plants do better-which in general means less opportunity for the algae plus there are fewer places for algae to grow. In addition, you can ease back the photo period without slowing down plant growth by much, yet really taking the algae out at the knees.

Just my 2c

Steve001 12-06-2012 03:31 AM


Originally Posted by Itwasntme (Post 2094333)
micheljg: They are actually these but there is nothing special to know.

Steve001, do you think its PAR what makes the difference? Unfortunately I cant get PARmeter. Is it possible that leds have more PAR/PUR than T8s but still "less powerful" to grow algae?

I think so. Sorry, that I can't be more helpful.

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