Help/advice concerning bleaching corals

[serbusfish]

First of all the important details:

S.G 1.025
MAG 1410
Calcium 400
KH 9dkh
Nitrate 0.5
Phosphate 0.03
Light duration 7 hours (full intensity), 10 hours including ramp up/down

I am having problems with a few of my corals. I have an unknown species of Acropora that is bleaching in random places + a Lobo that seems to be in the process of bleaching too. I dont know why this is happening, the only thing that has changed recently is I cleaned my powerheads and now they are performing much better. The Lobo is getting medium amount of flow and the Acro colony along with my other SPS are getting a higher amount of flow (all other SPS which include Monti's, Birdsnest, Elephant Skin, Acropora Florida, Acropora Slimer, and Acropora Tenius are doing fine and showing growth).

I also replaced my 4x T5's with a 320w Maxspect Razor LED light on 24th September, I have slowly increased my light intensity from 40% up to 85% (for the blue channel, white channel remain at 45%). I have a lot of corals doing well (Goniapora, Elegance coral, Fungia, Torch, Acans, Trachyphyllia, Bubble coral) so I am really confused as to why these specific corals are bleaching.

I took some pics with the tank light off, I can take some later when the lights are on:

 

[username in use]

What did you clean the powerheads with?

 

[serbusfish]

What did you clean the powerheads with?

D-D Ezeclean. Soaked for 3 hours then rinsed in RO water.

 

[serbusfish]

Bump

 

[kevincp]

I try not to get into discussion here, cause i don't want to give advice and not have it work, but i have couple questions, first how old is the tank, took myself a couple years to get it stable to grow, SPS coral right, also LEDs put out a very powerful light and everyone thinks you need to turn them up slowly until they can get it to full power, Thats not true, "myself included thought the same thing." We currently run our LEDs at 45% and get growth that you can see daily, when we frag they will encrust within 2 to 3 weeks, we run your tanks at 77 degrees PH 8.32 Calcium 420 mag 1380 and our KH 10.5 to 11.2 we don't even bother checking Nitrate or Phosphate that much anymore, no dosing, no feeding we run calcium reactors with 1% magnesium 9% Caribsea ARM Calcium Reactor Media, we supply the tanks once a week Red Sea Reef Energy A & B, and really don't mess with it, most important 10% water change weekly, SPS like clean water, your going to lose some ,so hang in there it take time

 

[serbusfish]

I try not to get into discussion here, cause i don't want to give advice and not have it work, but i have couple questions, first how old is the tank, took myself a couple years to get it stable to grow, SPS coral right, also LEDs put out a very powerful light and everyone thinks you need to turn them up slowly until they can get it to full power, Thats not true, "myself included thought the same thing." We currently run our LEDs at 45% and get growth that you can see daily, when we frag they will encrust within 2 to 3 weeks, we run your tanks at 77 degrees PH 8.32 Calcium 420 mag 1380 and our KH 10.5 to 11.2 we don't even bother checking Nitrate or Phosphate that much anymore, no dosing, no feeding we run calcium reactors with 1% magnesium 9% Caribsea ARM Calcium Reactor Media, we supply the tanks once a week Red Sea Reef Energy A & B, and really don't mess with it, most important 10% water change weekly, SPS like clean water, your going to lose some ,so hang in there it take time

Tank was cycled in March, I dose calcium in liquid form, and I run ROWAphos to keep phosphates down. I feed corals NYOS reef pepper twice a week. I do a 15% water change weekly.

 

[kevincp]

Well it sounds like the tank is right , i would try slowly to raise you alkalinity and try to bring it up, what kind of salt do you use? we use Reef crystals, most Local store including us run high alkalinity. and we have had trouble bringing in corals to our tank that have been in low KH tanks good luck

 

[BigJohnny]

This has nothing to do with low alk (9 is not low for .03 phos and .5 nitrate). You also want to keep alk as stable as possible when a coral is stressed (and in general). Have your params always been there and stable?

This was likely a result of the new lighting since it was the only recent significant change. You only have issues with 2 corals so don't go drastically changing the whole tank. I'd reduce the intensity of the leds and see if that helps, it won't hurt your other corals. Give it a few weeks at reduced intensity or photoperiod.

Don't freak out, acropora can die randomly when everything is seemingly perfect. The fact that the Lobo is bleaching as well leads me to believe they are both just reacting negatively to the light.

If you start getting more bleached corals even after reducing light, then it might be something else. But IMO your parameters are great, just keep them stable and try the reduced intensity or photoperiod