What causes sps coral to brown out?

So just was curious what causes this? Trying a couple of different sps corals in my tank now and in the the past they have either starting losing their flesh from the bottom up or turned brown and died. Is the browning caused by too much light or not enough, trace elements not at the right levels, or not enough flow or too much? Right now levels in my tank are cal 420 alk 10 dkh and mag 1250. Also what does RTN refer to? I have heard it before and curious what it means.

Thanks for the Alk, Ca and Mg levels.
Show us a pic of your tank and answer the questions below and we will help you keep SPS colorful.

What is the size and age of this tank? Is it the 100 gal just started?
Does it have a cover or is the hood completely closed in?
What lights?
What is the filtration?
What is the temperature and salinity?
What is the maximum temperature in the PM?
Does the pic(s) show the nozzles and powerheads so we can see the flow?

Oh and that's necrosis not narcosis. All it means is that the tissue is dieing back quickly or slowly, nothing more. It can be caused by all the things you mentioned... and more.


Edited by Mark Peterson - February 12 2011 at 10:39am

^ He nailed it. Not enough PAR, not enough flow, excessive nutrients or all of the above. Like Mark mentioned if you can post a pic it would help us out a ton. 

It definitely sounds like you need more light. Heat will completely negate the benefits of T5's. The more heat, the more resistance thus much less PAR is produced. We'll be able to tell much better when the pic gets posted.

Strange thing is I have had some orange monti that after slowly moving it up in my tank when it got to the top 1/3 it bleached out on me. Moved it back down and seems to be getting it's color back. I know monti is not very light intense coral but the bleaching happened within a couple of days. Would that still happen if the lighting was lacking? Also I'm more than a little confused on flow. In a lot of places in the tank I have a hard time placing lps corals. Seems like the flow is too much and they won't open and extend. This is where I have ended up placing most of the sps figuring the higher flow would be better for them. I guess I should be a little clearer on the browning out. I have around 7 different frags of sps in there now and none of them have browned out yet. In the past I have had several that have browned out. Of course I have changed several things in the tank since then. Just was curious what caused it and ways to avoid it this time. I really appreciate all the feed back you guys are giving helping me understand a little better. As far as export goes I am running a dsb, rubble rock, and cheato in the sump. Forgot to include that in my other post. All the N's are at 0 every time I test. Never have tested for phosphates though. Water changes about once a month maybe less. Dosing alk, cal, mag and iodine. Thought about strontium and potassium but don't have a test kit for these. Makes me nervous . For fish I have tailbot damsel, sailfin tang, potters angel, potters wrasse, melanarous wrasse. Feeding is about an 1/8 of a cube of emerald entree or mysis or brine every day at night. One capful of Aqua vitro once a week and either oyster eggs or zooplankton once a week around 1 or 2 teaspoons. Mix in some frozen baby brine shrimp every once in a while. The lps in the tank are exploding with growth right now. Have candy canes, acans, blasto's, and zoo's. Also guess I should say since changing the rockwork in the tank to allow better water movement my pink bird's nest has really started growing. So maybe the changes I made have helped and I'm just being a sissy worrying about this.   Anyways thanks for all your help guys and sorry for the long post. Will post pics when the lights come on.

Something there is bothering me. Can't quite put my finger on it, right now. I'll come back later.
Can we see a pic of underneath?

Here you go Mark.