Help with bleaching SPS

[DenverAcro]

Well this is my first post here and I am in need of a little help. Let me preface with specs and parameters:

125g set up 8 months ago with 50% Live Rock & 50% Dry Rock.
6 G4 XR15w Pro's at 36% overall intensity 12 hours total light with 220 PAR peak. UV 50%, all blues 100%, 10% warm & cool whites. 2hr ramp up & 2hr ramp down.
Temp - 77-78F
Salinity - 1.0260 (stable)
PH - 8.0-8.4 (night to day)
Alk 8.4- 8.6 (stable)
Ca - 410-420 (stable)
Mg - 1500 and naturally decreasing
No3 - 5-10ppm
Po4 - undetectable to .010 (GFO)
Ammonia - undetectable
Nitrite - undetectable

Over the past few months I have been losing my acros due to bleaching (top down). The frags will look great for a week or so then will begin to bleach and after that begin to RTN. At first I thought it was my lights (G4 XR15w Pro), so I Invested in a Par Meter (Apogee SQ-520) and found I was peaking at 300 PAR (not that high, I know). I turned the lights down and my UV to 50% so that my peak Par is now 220. I was dosing NoPox but stopped thinking the carbon was overwhelming the corals, so I switched to 15% water changes every 3 days in lieu of carbon dosing. ICP tests reveals nothing outside of the norm. No flatworms/eggs seen (and I've looked plenty). I had a bout with red bugs awhile back but interceptor took car of that. I have been fighting cyano and hair alge since the beginning, but have kept it at manageable levels with manual removal of the hair algae and chemiclean about every 3 months or so. I should mention that my acros that have been in the system since the beginning are showing no stress at all and are fully colored and growing like weeds. I'm at a loss. . . Any help would be apreciated.

 

[Ashish Patel]

I thought 300 PAR was nothing but its prove to be too much, especially coming from LEDs. Spot light PAR is more deadly then a blanket of light!. I would frag those corals that are bleaching since chance of them healing on their own is 0%. The frags should recover nicely as long as you put them in lower par (150-200) and let them recover their zoozethelle.

Overall your parameters look good but I'd say your phosphates are probably causing problems along with your lighting. i've had corals bleach when phosphates went to 0 for more than 2 days, but never had them show any signs of stress when above .10. So now I just have phosphates anywhere from 0.03-0.09 before taking action - my action would be adjusting the skimmer line or removing cheato, or even increasing flow. Also pay more attention to your light acclimation and get 3 turbo snails to take care of that hair algae.. Hope this helps..

 

[markalot]

Besides dropping light levels I would slowly lower KH down to 7.5, bad things seem to happen slower at KH levels closer to NSW, especially if nutrients are super low. For PO4, you can buy Seachem Phosphate for freshwater planted tanks and dose a little just to keep from bottoming out. Keep in mind you have ehalthy colonies so make changes very slowly.

It's not unusual for new frags to suffer while older colonies do not. Healthy acros can put up with a lot while new frags tend to be stressed and can't tolerate much.