SPS corals turning brown

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Eilat Israel
Shalom
My SPS corals are turning brown,But this is not affecting other corals in the tank like my brain corals or my zoas or my clams.
My parameters are all in range Tested with Red Sea test kits.
NO3 0.5
PO4 0.02
SG 1.026
NO2 00
NH3 00
Ca 480
Mg 1280
T'C 26/27 C
Any Ideas are welcome
 
Flow and lighting?
 
Strong flow all SPS corals in upper half of tank.Tank is 90x60x50 and has 9x T5 39w lamps from ATI and are as follows
6x Aqua blue
2x Blue plus
1x True actinic
Lights run from 1400-2300 with timers switching them on at different times,maximum light for about 6 hours.
 
How often do you do water changes?
Your magnesium a bit low, ideally it should be 1380ppm. Your NO3 and PO4 might be to low, that can affect SPS development.
Which colours sps do you have?
 
Definitely not a case of too low Mg, but yes in terms of balanced to Ca, it is low, but I would rather allow Ca to drop to the 390 to 420 mark, as there is no benefit in keeping Ca above 400ppm.
Too low nutrients will hardly cause sps corals to turn brown, as it is usually a function of zooxanthellae population density increasing as a result of available nutrients that causes brown corals. Or, insufficient lighting, which does not seem to be the case here, assuming bulbs are in decent reflectors, even not, you should have sufficient light.
A No3 of 0.5 and PO4 is more than sufficient to brown out sps if combined with regular and excessive feeding.
Are you dosing a liquid carbon source such as Nopox?
Colorometric hobby grade test kits, whether they state "pro" or not for PO4 is not nearly as accurate as we need, so your PO reading is merely an indication that it is there. Rather bring that and your NO3 down to undetectable levels and feed your fish and corals.
Your tank dimentions are very similar to mine, in which i am running Flow at about 120 tank volume turnover rate, about 25 000 litres per hour.
When you say high flow, please elaborate.
You also did not mention your alkalinity?
 
Just something extra on the lighting i've found, If the tubes aren't in an actively cooled housing & the ballasts start to get too hot (above 70c i think it is) they will back off output.....I've seen myself switching from non cooled housing to cooled housing a par increase of close to double so just because their ati tubes won't mean a lot unless there in a decent actively cooled unit,in my case it was double par shift going from a redsea s650 t5 light hood to a Ati sunpower.
 
Water changes once a week 10% ,3 wave makers that run on 3 hour cycles.The biggest one is 12000l /h and the other two are 6000l/h.My pump is 7000l/h and my Alk is a Kh 0f 8
 
Please explain the three hour cycles
 
Cycles run through timers 3 hours on 3 hours off always changing sequance,as to fitting 9 t5 tubes in easy home built cover that was designed down to the last mm still planning to install two rows of 150000K white LEDs and 4 blue LEDs as night lights
 
I Think Temp to high at 27, drop to 25.5. Secondly drop Calcium to between 400 and 420 and magnesium up to 1350. Keep it Stable.
Maybe run lights extra 2 hours full light for a month and see what it does, with a two hour sunrise/sunset either side.
feed your corals or feed your fish more nitrate maybe a bit low.
 
See this is an old thread but , low nitrates and phosphates will brown out most sps - montipora excluded these just seem to fade.

I would aim to keep No3 @ 2-3 ppm and phos at detectable levels . I see no mention of alk this should be stable at 7,5 to 8.5 .

I am currently having to add potassium nitrate and RS amino's A+B in my coral only tank to get colours back.
 
Not really all except one SPS corals returned to the sea the single one is still brown but has grown 4mm in the last 2 months.all the coral showed growth.Am going to upgrade my lights to a DIy led fitting and then will go and get new corals and will see what happens.As for the ones I returned to the sea a week later they where coloured up again.
 
Do n't know but the corals came from the sea here and 90% of my other life stock as well so it makes no difference if I return them or not.
 
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