Radion LEDs causing corals to fade/bleach...help!!

[rampro6698]

I have a 12 foot long 600 gal reef tank that is about 2 years old. It has 10 Radion LED fixtures spaced over it about 10" above the water level. The tank is 30" deep with about 4" sand bed. I have had problems with all my corals looking a little faded and a few bleaching white. I do not have a large amount of coral in the tank as I am trying to iron out this problem before putting much more money into this.

My problem is that I started my LEDs with the radiant color template at about 65% max daytime intensity (lights come on at noon with a very faint blue light and ramp up over the day and then back down and go to a very low blue light at 10pm and then off completely at 11pm). This caused obvious fading so I decreased the intensity to 40%. I have gradually been decreasing the intensity over the last 18 months so that it is now at 25% max.

That means with the current template and lighting schedule it only is at that intensity for about 2 hours each day. The rest of the time prior to and after those two hours it is going up to or decreasing from that intensity per the schedule. I have tried a couple of other templates with similar bell curve shapes over the lighting period with no real change. I have noticed many of the corals coming back into normal color but overall there is still general fading. The monipora and acropora corals are growing but still seem slightly faded. I know there are many variables that go into a reef tank and I can answer about any specifics that I know if someone asks. Water parameters as follows:

SG 1.025
Ca 400-425
Mg 1350
dKH 10
water temp 79 F
Nitrates and Nitrites undetectable
Phosphate and Silicates undetectable
Main display tank is approx 590 gal and refugium about 150 gal and sump about 150 gal
ozonizer running with reading of 350-400 mV

My main question is: has anyone else gotten to a point where they are turning their LEDs down to 25% or lower for the max intensity? I have called Ecotech marine and they don't really have an answer other than to turn them down more and see what happens. Just open to some ideas or see if anyone else has had this problem.

 

[dillct]

Zero phosphates/nitrates along with high alk = bleaching, no growth and dead corals.

Nothing wrong with your lights and I'm no Ecotech fanboy.

 

[theatrus]

Corals will often become very pale in the absence of any nutrients - how undetectable is undetectable? It may help to actually increase nutrients.

 

[Wazzel]

With your lights that low it is not them causing the bleaching. I suspect lack of food.

 

[Tweaked]

Yep, low nutrients and high alk is a no-no. Lower the Alk and feed a bit more. The Radions can produce some amazing colors which I've seen with my own eyes. And lower the alk slowly

 

[rampro6698]

Zero phosphates/nitrates along with high alk = bleaching, no growth and dead corals.

Nothing wrong with your lights and I'm no Ecotech fanboy.

When I say undetectable I mean the Nitrates are 0-5 (very faintly pink on a test strip) and Nitrites show no color on the test strip. Phosphate stays at the base color with two different brand test kits (so lowest level the kit would measure). I tried running the alk at about 7-8 (more what natural seawater is) and my LFS guy that set up the system said to run it closer to 10.

Maybe you guys are on to something here. I don't have near the bioload that this tank/skimmer setup can handle and don't have that many fish. Feed the fish once a day. I do feed the corals once a week but only started that about 2 months ago (focused feeding with a pipet syringe).

Good information. Keep it coming. Thanks!

 

[rampro6698]

Yep, low nutrients and high alk is a no-no. Lower the Alk and feed a bit more. The Radions can produce some amazing colors which I've seen with my own eyes. And lower the alk slowly

I will try SLOWLY decreasing the alk. Any suggested target for the alk?

I will try feeding more too and maybe slowing increasing the lights. Probably will make one change at a time to avoid confusion.

 

[theatrus]

I try to keep around 8dKh / 140ppm.

(This is not to say I'm good at keeping it there, currently at 120ppm since the Ca reactor isn't keeping pace :-X)

 

[rampro6698]

With your lights that low it is not them causing the bleaching. I suspect lack of food.

So here is something I can't really figure out: I have always read that SPS corals like acroporas are more difficult to grow and sustain in marine aquariums compared to LPS types, etc. If my problem is lack of food and lack of nutrients, why are my acroporas and montiporas growing and other corals not?

 

[Tweaked]

I will try SLOWLY decreasing the alk. Any suggested target for the alk?

Of course I do.. what does your salt mix at? When I mix salt, I like the big three to match my tank which ensures a less stressful change for all involved. Salinity, Alk, and temp. My salt mixes on average at 8.1 and I keep my tank around 8.2. This has been a good number for my acros, and I have room to drop or raise in case of a malfunction in dosing pumps.

 

[Wazzel]

So here is something I can't really figure out: I have always read that SPS corals like acroporas are more difficult to grow and sustain in marine aquariums compared to LPS types, etc. If my problem is lack of food and lack of nutrients, why are my acroporas and montiporas growing and other corals not?

Not enough food. LPS do better in systems with more food. SPS pail, LPS not growing. Your tank sounds hungry.

 

[rampro6698]

Not enough food. LPS do better in systems with more food. SPS pail, LPS not growing. Your tank sounds hungry.

I will try slowly reducing the alk as you guys suggest and maybe feeding fish and coral more. One thing that is still weird about this: I have a brown dusting of stuff all over the gravel bed which I assumed was brown algae or diatoms. But I always thought diatoms only occurred in a fairly nutrient rich environment or in tanks in which something was "out of balance" with regards to pollutants vs skimming vs water changes, etc. So if my tank is so "clean" then why do I have this diatom issue?

 

[Wazzel]

How much flow do you have? Can you post a picture of the brown dust?

 

[rampro6698]

How much flow do you have? Can you post a picture of the brown dust?

I will try to post a pic in a day or so. I have one MP40 powerhead at each end of the tank and one Tunze 6125 powerhead at each end. Plus 3000 gph flow from the overflow boxes return. So that is 15-18,000 gph flow total. The water moves pretty vigorously through the tank but it does seem that this stuff accumulates more where there is less flow. I have tried positioning powerheads closer to the bottom but I get too much sand getting blown up from the flow. So the lower 1/3 of the water column probably could use more direct flow I am just not sure how to get that. I have looked at wave boxes but I think the tank is just too big/long (12 feet long tank) overall for an effective wave. Plus wave boxes are noisy.

 

[nikon187]

Test strips?? those are very inaccurate in general, i would use a quality liquid test to confirm

 

[Wazzel]

You may have flow issues. If your tank is 12 foot long and all your pumps are on the ends you could have dead spots. You run 25-30x's turnover in your tank. I run 50-60x's and actually think I could use more. SPS need lots of flow. The stuff you see could be detritus settling out. Without seeing it in person I do not know for sure.

 

[Spartanman22]

If you say you're tank is on the lower bioload side an easy way to increase nutrient input would be the addition of more fish, plus then it's an excuse to buy more fish! I was having similar issues. Coral growth was good but color was paling. I got my alk dialed in at 7.3, and added a few more fish to the mix. I also setup an automatic fish feeder to provide more of a nutrient input throughout the day while I was away at work.

 

[Wsufan18]

There have been posts lately making the case that the "cleaner" water intensifies the par of light. Uln tanks seem to need lower light intensity compared to a tank with detectable po4 and no3 or corals will fade/bleach. 600 gallons is a lot of volume for a small bio load. I would try skimming periodically, increase fish( buy cheap chromis school...etc) keep lights at 25% until alk is lowered and po4 , no3 bumps up some. Then gradual light increases of 5% per week.

 

[rampro6698]

Test strips?? those are very inaccurate in general, i would use a quality liquid test to confirm

I did actually order two separate Elos brand liquid test kits, one for nitrate and one for nitrite. I have been using two different liquid test kits for PO4. How are you guys all measuring down to two decimal places even with the liquid test kits for nitrate, nitrite, and PO4? I mean these kits still go by a color range and I see people all the time posting get your PO4 at .02 to .08 but not above .10, etc. How are able to get a reading that accurate? What test kits are they using?

 

[rampro6698]

You may have flow issues. If your tank is 12 foot long and all your pumps are on the ends you could have dead spots. You run 25-30x's turnover in your tank. I run 50-60x's and actually think I could use more. SPS need lots of flow. The stuff you see could be detritus settling out. Without seeing it in person I do not know for sure.

I do probably have some dead spots near the center of the tank and other areas. I don't think this is detritus though because when I gravel vac it doesn't come up like fine dust. It is actually heavy enough that some just circulates in the syphon and falls back down. Some smaller pieces do come into the syphon but that is why I suspect it is diatoms. Problem I can't figure out is that everything would suggest my tank is "too clean" and does not have enough waste/nutrients, etc. And my lights are pretty low as it is. So how are diatoms growing? If it is detritus, then why does my tank seem to be too clean for coral growth with no real detectable nitrates and PO4? I will see what the dedicated liquid test kits show but I just can't figure out this brown covering. I will try to post some pics. I am slowing lowering my alk.