Fin Rot?
My husband has a 50 gallon saltwater tank. Up until about 3 days ago, he had 
a black and green Nudibranch in the tank. Unfortunately, this poor creature 
met his demise when he got sucked into the power head.
I'm not sure how long he was stuck in the powerhead, but I came home and 
noticed that everything did not "look right" with the tank. That is when we 
found the Nudibranch and promptly removed him. At the time that we found 
him, we also noticed that all of the fish were stressed and covered with what 
looked like freshwater aquarium "ick." There are two blue/yellow damsels, 
one domino damsel, one yellow tang, and a clown fish in the tank. At first, 
the domino damsel seemed to have suffered the most. His fins were tattered 
and bloody and he had a white "covering" on his eyes. Soon after, the clown 
fish and one of the blue/yellow damsels were affected. The tang developed 
clear, blister-like nodules on his fins (excluding the tail and dorsal fins).
We have done a 25% water change and yet the "fin rot" seems to be getting 
worse. The tang now has no flesh to speak of on his fins...there is nothing 
left but bone...and his dorsal fin and tail are showing signs of infection. 
My first thought was that the Nudibranch released a "poison" into the tank 
when he was chewed up by the powerhead. Am I correct? If so, what action 
and/or treatment can be done to clear this up before all of the fish are 
affected and killed? The biggest problem is that my husband also has 
anemones, tube worms, sponges, soft corals, and other invertebrates in the 
tank. Whatever is in the water seems to be affecting EVERYTHING and we don't 
have a hospital tank. PLEASE help us...give us some advice...something to 
try!
Thanks, Gina and Dane Gerdes
>>
How much made-up synthetic seawater do you have on hand... Change ALL or as much of the water as can be removed and replaced to have all your gear still working (i.e., if only half the tank can be refilled, but all your filters, pumps, heaters work, do so). Do you have any chemical filtrants like activated carbon on hand. Do place that in your filter flow paths...
You've noticed how distinctive Nudibranchs are in "wild" photographs? And how slow moving they are in captivity? Yes they are bundles of noxious materials... as part of their involved defense mechanisms package... 
Here's hoping that the massive dilution and absorption saves the rest of your livestock. Good luck to you.
Bob Fenner