bleaching then death?

[Black71gp]

what causes or what are the causes that can cause major bleaching and then death in corals.. i was at a swap two weekends ago and have most of the corals i got there other than two blue stags, then i also lost a few sps that i had in my tank before.. and a few other things.. non sps. but what causes the bleaching then death that spreads through the whole coral even if fragged off...? well could not frag much they were already frags....thanks.. well i am thinking its stn or rtn.. based on some change.. maybe an alk swing? dont know loking into it..
jarrod

[Mike O'Brien]

It really could be alot of different factors. More info about how the frag's were introduced and about you're tank will be needed to try to pin it down. RTN and STN really don't mean anything. Only that the coral died slowly or quickly.

[Black71gp]

some have been in the tank for months others were drip aclimated for an hour or so..

[Casey]

could be anything that could be stressing the corals out its even happening in the wild.

[skeety]

Some causes I know of:

#1 cause...Stress (as Casey stated). But more specifically:

Instability of parameters. Constant swings in temp, salinity, unusual pH, etc can all cause stress to the coral and the zooxanthella that inhabit it. This can lead to bleaching and death.

Insufficient lighting. If the coral doesn't get enough light, it can starve. It's symbiotic zooxanthella can starve. The coral will then bleach and die.

Chemical warfare. Nearby corals can start a chemical war. coral killing toxins can be release, sweeper tenticles, or actually ingesting the other coral, can lead to bleaching and death.

Inproper flow. Not enough flow can allow buildup of detrius/wastes/poop/etc and suffocate the polyps in that area. They bleach, algae takes over that area and it can spread from there.

Nutrient issues. Although indirect. But high nutrient issues can lead to algae problems that can then spread/grow near the coral, causing competition, reduction in lighting, or even aggressive growth overtaking the coral. Phosphate problems I don't completely understand (wicking), but poor nutrient exporting can cause increased phophates which can cause bleaching/death.

Nipping/picking/eating. Fish nipping at corals can cause them to keep their polyps retracted. Which cause loss of gas exchange, poor dietary retrieval, etc. Predetors like Parrot fish or some crabs/polycheates/nudi's/flatworms can actually eat the coral tissue. Killing the coral.

Abrasion/breakage. In a healthy tank, SPS's usually recover quickly from being bumped/broken. But still..any tear in the coral's tissue is opportunity for infection. If it's minor, it's not usually a big deal...but if a large scrape or non lateral break is made...sometimes supergluing the wound (think of it as a band-aid) can help minimize the risk of infection.

Chemical. Most people know that copper is fatal to corals. But in case you didn't, it is in more than trace concentrations. Other chemicals can ALSO poison/kill the coral. Also, (kind of related to the previously mention nutrient problem), higher than ideal levels of Nitrates are harmful to most corals. Ammonia is extremely toxic, as are nitrites. But any number of chemical issues could be cause for bleaching as well.

Those are a few of the most common reasons for coral bleaching that I'm aware of. I also listed them in what *I* think is roughly the order of likelyness, based on how commonly they turn out to be the reason.

If anyone can think of others please chime in. i think this could be a valuable research thread.

If I made a mistake or provided misinformation, PLEASE feel free to correct me.

Good question for this forum!!!

[Twitterbait]

on a side note... you only need 1 polyp on a frag to keep the coral alive. I had a single fall into some eggcrate and it took off and has grown into a nice colony since

if the small frag is dying, chop the tip and set it in a small eggcrate square (don't glue it or it will die).