Sick Fish (White Growth on Fins)

[Palster]

I currently have several fish with a white growth on the end of their fins. My puffer has had this for a while and does not appear to be getting any worse however my Clown Trigger and Niger Trigger are actually starting to lose parts of their fins from this. I have done a lot of research on this and from what I can tell this does not appear to be Lymphocystis. I lost a couple of fish a few months ago from this "disease" and I do not want to lose anymore. All of the other fish in the tank appear to be fine.

My tank (180 gallon) has been running for about 6 months and was seeded with live rock and sand from my previous 90 gallon. Ammonia and nitrite are zero. Nitrates are 25 ppm (tested with a Salifert test kit). This is a predatory FOWLR tank so I am unable to get the Nitrates any lower however I do not think this is too bad for this kind of tank.

The research I have done would indicate this is some kind of bacterial infection which is usually caused by poor water quality however as stated above my water quality does not appear to be too bad.

The only thing I have done so far is to give the puffer and triggers a 10 minute freshwater dip with Maracyn Plus (antibiotic) in the water. Also, all fish were quarantined prior to introduction into the main system.

Any suggestions? I have considered doing massive water changes with the hopes of diluting out whatever is causing this. The only other thing that occurred to me is stress but none of the sick fish appear to be stressed and are not being bullied by any of the other fish.

I will try to add a picture of the fish later today however I wanted to get the post up first.