LED tank - Acro turning brown at the tips

[Kahuna]

I recently installed an excellent DIY LED array over my 90g. Initialy, I bleached several corals and turned the LED's down so that the corals would recover, which they did. However, I've some ORA frags that are going from blue or purple to brown at the tips. Too much light? Not enough? PAR is about 315-350 where they are with the LED's at 100%. Probably at around 220 or so now. Photoperiod is from 0530-2130, with the LED's ramping to 20% 0530-0730, ramping to 45% 0730-0930, and then staying at 45% until 1830, which then ramps down over the next 3.5 hrs.

Please advise.

Thanks.

 

[Acrotrdco]

Given that your water parameter and flow didn't change after installing the LED fixture, and with sufficient PAR, perhaps it's the color of the bulbs you used.

What kind of bulbs did you use in your DIY LED fixture?

I've had great success when mixing 405nm SEMI violet + 445nm SEMI royal blue + 460nm Cree XP-E royal blue + 480nm Cree XP-E blue bulbs to complete the full blue spectrum (just missing 420nm now).

The blue / purple tips of my acro had been coloring up really well, see here:
Purple -

Blue -

 

[Kahuna]

They are Cree XR-E Series RC Cool White and Cree Royal Blue, with 8 Cree Reds in the mix for sunrise and sunset. The flow changed, as I went from 2 Koralia Evo 1050's to two Vortech MP40's.

 

[Acrotrdco]

To be honest that's too much red.

I'm only using 4x Semi Red LED in my 65G and I think it's just right, perhaps cut down the red from 8 to 4, and replace them with Cree XP-E blue (480nm). See if that helps.

p.s. are you using any purple (i.e. 395-420nm?)

 

[Kahuna]

No purple. My reds ramp up from 0 to 70%, hold for 15 minutes, and then reverse the ramp at sunrise and sunset, so twice a day. They are also on for about 3 hours at 40% during the noon phase. Is this bad? No violet.

 

[Acrotrdco]

Well, red light is gone some 10-15 meter under water, so mimic sunset/sunrise/noon with red light is really not needed, except for aesthetics.

I'm only using very little red to produce the KZ Fuji Purple T5 look, and it's doing a pretty good job at that.

You might want to think about adding 395-420nm violets and 480nm blue/cyan, I'm pretty happy with the results.

By the way your photoperiod is some 16 hours and imo it's way too long. I'm currently running:

Blue/violet only: 13 hrs, 12:00pm - 1:00am
blue + white (blue:white ratio 3:2): 9 hrs, 2:00pm - 11:00pm
all on (blue:white ratio 2:3): 5 hrs, 4:00pm - 9:00pm

With regards to PAR, this is the PAR reading of my tank when everything is turned on:
http://www.reefcentral.com/forums/showthread.php?t=1965294