Hi Stace,
Thanks, this clears up a lot of mistaken assumptions on my part when I wrote to you.
Here's my take:
It's unlikely that a coral would stage a comeback based on reliably constant energy input (lighting, in-tank nutrition) and tank params, then falter without a nwewly introduced external stress
If you do have a case of RTN (whatever the heck that really is --I'm starting to doubt my own definition), I rather prefer the Borneman-Lowrie line of thought, which proposes isolation of the affected coral. Their theory is that non-bacterial, external stresses trigger 'RTN', so if you give the coral its own volume of new water, you eliminate the trigger for 'RTN'. They also suggest dilution via water changes in-tank can alleviate the pressure on the afflicted coral. If they are correct that bacteria are never the causative agent, then Chloramphenicol is nearly useless, save against secondary infections.
Moreover, that antibiotic can be hazardous for some individuals, and is definitely hazardous for many useful bacteria. I'm not just talking about nitrifying and
denitrifying bacteria. The more benign bacteria that Acroporiids farm in their mucus aren't just a food source, but they also resist colonization by more overtly harmful bacteria. Granted, if the mucal fauna was already imbalanced/compromised, then I myself might be tempted to wipe the slate clean with antibiotics (in some treatment tank). However, antibiotics used improperly merely create resistant strains of the very bacteria we wish to suppress.
Here's what I would do, if I caught RTN in time:
Move the coral head to a completely separate volume of water. If I felt that a bacterial infection is present, then I would chance a prior antibiotic bath or better yet an iodine-solution dip in a separate container before the transfer. I would make sure the new volume of water had top-shelf params and lighting. If I knew a reliable Acropora food item, I would provide it (GP?). When the tissue recession is reversed, and the damage undone, only then would I consider returning the coral to the display.
If one of Eric B's suspicions is correct, that chemical aggression from neighboring coral is a trigger (and bacterial infections are merely opportunistic), then the returned, healed coral has the possible benefit of learned resistance (or immunity if you will) to such stresses.
No harm in whipping up a fresh batch of saltwater and ageing it. No harm in isolating the affected coral.
HTH, and I hope others with experience beating coral tissue recession will comtribute their views.
horge
[This message has been edited by horge (edited 09-27-2000).]
