what causes bleaching and browning- light/temp?

[tomtoothdoc]

[FONT=&quot]i'm still somewhat confused about the bleaching/browning phenomena. is it mainly lighting issue or temperature issue?[FONT=&quot] (take out phosphate as a variable.)

(lets take the phosphate level out of the equation for this situation--assume it is at the same level all the time) if i have a predominantly purple color acro( that has been in the same location for say 2 months) and it turns brown, can that be because of too much light or not enough light?...what mechanism causes the purple zooxanthellae to appear brown?
what about bleaching? is it from too much light or can it be from not enough light also?
do temperature swings play a role in these events(bleaching/browning)?

i have some chalices that were quite colorful. they started to loose their colors and are beginning to bleach. they have been in the same location for at least 6 months. i did change the bulbs 2-3 months before the bleaching started and the only other thing that was out of the ordinary was that i had the circuit breaker tripped from a chafed/exposed heater wire in the equipment room for half a day. that shuts down the return pumps, skimmer, 2 parts dosers, heaters, gfo reactor, fluval 405 running just chemipure plus the return to the remote refugium. the display tank's equipments (lights, flow, spare heater) on a separate circuit were working normally, the only thing different there was the return pumps were not on. the temp went down from 78 to 71 when i got home. the defective heater was removed and power restored to the equipment room.

what should i do/if anything? should i move them to area with less light?(i have 2x400w 20k mh's and 2x110w actinics vho's on a 48x36x27...the mh bulbs are about 18" above the water) should i move them to the frag tank with 4x 24w t5's?

any idea/feed back would be appreciated. thanks, tom
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[juiceguy]

IME the purple/blues/pinks require the highest lighting...for example i have a wild caught bonsai that i fragged. 1 frag i placed next to the mother colony and it retains all the coloration. the other 2 frags i placed on a frag rack that receives indirect light and those frags are looking brownish rather than purple.

 

[KathyC]

I realize you are saying to take phosphates out of the equation, but if you have any more than an 'acceptable' level in the tank, even if it were the same stable level, and that level is too high, it will affect the coral.

Corals that were in the tank for a longer period of time may not show as much of an effect from the phosphates are a new coral that wasn't used to them being present at all.

 

[nyfynest22]

does lighting pay a factor in this ? or maybe alk swings? good question tom, dieing to see what everyone thinkss

 

[batt600]

Hi salinty will cause bleaching and yes the light would to if its to much light for the tank. copper in the tank will do it to if it very little. I went throw this with my tank only a few corals started to bleach and evey thing else was fine had to do a few water changes for thing to come back to color. A because a few penneys were in the tank.

 

[thesauce]

Photo period may also play a role. Cut back a little bit and see how things go.

 

[MIKE NY]

there are alot of factors that can cause bleaching and browning....for me it has always been a process of elimation to determine what may have caused it.....sometimes with some corals I never know. One thing I do know works for me is lowering a bleached coral helps regain color and slowly raising a brown out will help color it up again as long as all other parameters are in check....temp,same lighting, alk, mag, cal etc.....

 

[bizarrecorals]

what you should do is keep your water perm at the right level, than worry about everything else. A lot of people assume the brighter the light the better, thats not true, most bleaching of corals are caused by bad light acclimation and TOO MUCH LIGHT, it dosn't mean the more light you have the better, really depends on the species. Even if you have the same species, they may come from different place at different depth on where they were collected, and I wouldn't exceed 1.028 on salinity.

 

[SevTT]

[FONT=&quot]i'm still somewhat confused about the bleaching/browning phenomena. is it mainly lighting issue or temperature issue?[FONT=&quot] (take out phosphate as a variable.)
[/FONT][/FONT]

LOTS of things can cause bleaching or browning events. Temperature swings (high or low,) too much light, nitrates, lack of certain trace elements, too much of certain trace elements, exposure to toxins from other corals...lots of stuff.

Best thing to do is to keep an eye on your water parameters, do a water change if you haven't done one in a while, and just keep an eye on the corals. Correct anything wrong and hope for the best.