Για ρίξε μια ματιά τι προτείνει η Tropica
http://tropica.com/en/guide/make-you...success/light/
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και κάτι καλό ακόμα
Without PAR meter you can only compare.
My advice which is by no means PAR tested nor substantiated is the following:
LED = 60%
T5 Flouro= 80%
T8 Flouro = 100%
MH = 150%
So in essence if you would usually use 100W of T8 then use 60W LED 
If you usually use 80W T5 then use 60W LED.
I guarantee that you will actually have more PAR than you had before (barring poor setup) but safer to have more and be able to raise the light to reduce it's effect than to have too little and not be able to do anything about it.
απο εδώ
http://www.aquascapingworld.com/thre...r-a-tank.7829/