Random RTNing am I nuking my tank with light?

[a.t.t.r]

I have a standard 20 gallon. with two xr15's ontop about 9 inches above surface with the diffusers. I was running a majorly white spectrum capping at all colors 100 percent at 80 percent max output for only a few hours a day and the rest being much lower. Things were going ok monti caps that are right under the light are growing like weeds even if the color isnt the best. But I would get random STN and RTN on acros after having them in the tank for about a month. Some halt and a small patch of skin regrows others just vanish.

Recently I changed to a mostly blue spectrum with a slow shift from 20k -16k lighting maxing out at 60 percent and then over the course of an hour and a half peaks to 80 percent with white ( I have some decorative algae that needs the white and I also like seeing my fish withouyt them all looking black) and then ramps right back down to a 60 percent 16k and fades back to a 20 k as the sunsets. Almost instantly I lost an acro and a stylophora developed massive tissue loss around its middle (base is fine and top is fine)

Par meter seems absolutely worthless It is an old apogee from the reefcentral bulk buy back in the day and the numbers I was getting are around 2-300 where the coral sits when lights at maxed out. I am now wondering maybe this old par meter just isnt cut for LED and I am nuking my tank? additionally could the few hours of white per day be throwing off the pigmentation of my healthy corals and causing them to produce more browns. ( maybe I should set my white period to actually dim the lights mid day.. I can see the fish algae gets some light but the corals wont be flooded with reds and greens ).

Parameters are all fine and I actually have to add phosphate to the tank. I do small daily water changes with IO salt. works out to be 50 percent every 2 weeks. Temp never passes 82.

Anyways those of you running xr15's what would you be doing for your SPS in 20 gallons.

Forgive the typing... on a cell phone

 

[CoralB]

Yes !!! I believe the term nuking with light could very well explain the issue. First why are you running two radions for a tank of this size . Second why are you running it a 80-100% .

 

[Spare time]

That seems way too low for par numbers with those two lights at very high intensities but I could be wrong

Could you also list the par meter model, your water parameters (nitrate, and phosphate) , and the flow setup?


I would predict bleaching, not tissue necrosis from light being too intense, as the light wouldn't kill the coral immediately, but could result in the zooxanthellae dying and the coral being bleached for a bit followed by death

 

[a.t.t.r]

Yes !!! I believe the term nuking with light could very well explain the issue. First why are you running two radions for a tank of this size . Second why are you running it a 80-100% .

Two because the shadows sucked with a single one and 80-100 because of the par results.

 

[Spare time]

I forgot to ask, what height are they mounted?

 

[a.t.t.r]

That seems way too low for par numbers with those two lights at very high intensities.

Could you also list the par meter model, your water parameters, and such?

I let my friend borrow it so will get the model off him. It is an OLD unit from maybe 2006-2008.

ph 8.2
alk 8
CA 460
no3 9
phosphate .005- .1
salinity 1.025-1.028.
Thats all I really test for,

 

[a.t.t.r]

I forgot to ask, what height are they mounted?

9 inches to avoid massive light spill into room.

 

[a.t.t.r]

A

 

[sculpin01]

Phosphate 0.05-0.5?

 

[thatmanMIKEson]

It sounds like high light not sure what the nutrients are at but they better be high..

 

[Spare time]

I let my friend borrow it so will get the model off him. It is an OLD unit from maybe 2006-2008.

ph 8.2
alk 8
CA 460
no3 9
phosphate .05-.5.
salinity 1.025-1.028.
Thats all I really test for,

I wonder if it needs to be calibrated or if this version is not very sensitive to much of the violet area like some older par meters.

What phosphate test are you using. Assuming thats not a typo, 0.05-0.5 is a massive range lol

 

[a.t.t.r]

I wonder if it needs to be calibrated or if this version is not very sensitive to much of the violet area like some older par meters.

What phosphate test are you using. Assuming thats not a typo, 0.05-0.5 is a massive range lol

I am dosing phosphate. .03 is average and my target.

 

[a.t.t.r]

It sounds like high light not sure what the nutrients are at but they better be high..

Nutrients are low but not zero. I struggle to elevate the po4.

 

[Spare time]

I am dosing phosphate. .3 is average and my target.

0.3 would be considered very high. Most people try to keep it between 0.03-0.01 (give or take some error in the kit)

 

[a.t.t.r]

0.3 would be considered very high. Most people try to keep it between 0.03-0.01 (give or take some error in the kit)

You are right. I just looked at my log and i was missing a zero... 0.03 with high of 0.1

 

[Spare time]

I'd highly recommend trying to use a different par meter.

Also, could you describe how the flow is setup?

 

[a.t.t.r]

I'd highly recommend trying to use a different par meter.

Also, could you describe how the flow is setup?

I have two nero 3's mounted on the back wall on the left and right far corners of the tank. Set to 0-70 percent flow with medium - high variability while lights are on. I get 0 sediment buildup anywhere in the tank (including behind the rocks) and only minimal sand pickup (front two corners blow a lil sand every now and then)

 

[X-37B]

Well after reading your build thread it looks like your system was nuked with alk in January and most everything died.
Not sure what happened after as the updates stopped.
Maybe you can update us.
2 XR15's, what gen?, are alot of light for that size system.
To many variable to comment on for me to be honest.

 

[a.t.t.r]

Well after reading your build thread it looks like your system was nuked with alk in January and most everything died.
Not sure what happened after as the updates stopped.
Maybe you can update us.
2 XR15's, what gen?, are alot of light for that size system.
To many variable to comment on for me to be honest.

Oh yeah that was corrected and most of the corals bounced back or are still regrowing.. The monti caps that i have had since the start have doubled insize since then and are now growing into eachother ( they seem to love what ever light setting i throw at them despite being centered under the xr15)
The lights are both gen 5 xr15 pros.

When it comes to everything else in the tank I pretty much know what I am doing I used to run multiple frag tanks and an LFS. It has just been years and the LED's are the only new element to me. When I left the hobby MH was king and T5's were just becoming popular and icecap ballast were king.

 

[thatmanMIKEson]

Nutrients are low but not zero. I struggle to elevate the po4.

Me too, I dose and check every 3_4 days