Lighting requirements for coral??? no growth

[aquablizz]

I have a 75 display tank which was fish only for many year.. water quality seems to be good with only coralline algae in tank.. running a fuge with macro as main filtration.

I introduced a few coral 3 months ago but have seen no growth at all yet still alive.
My only lighting is a 48-60" Current/Orbit for marine. According to the specs, the output in watts is only 46 watts.

Could this be the problem. the depth of the tank is 20 inches.
Thanks in advance
Blizz

 

[tdileo]

What kind of coral, where is it placed in the tank, and if its stony please let us know the calcium, alkalinity and magnesium levels of your tank. I hear the Orbit Marine is a decent LED but won't do much past a foot deep.

 

[tankstudy]

Based off the specs you only have 10 to 20 par at 18 to 21 inches of depth. You have 70 to 50 par at 12 inches down. You can probably grow low light coral at the 12 inch depth marker but not much is going to grow below that. Your light is too weak.