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I need some help from the experts. I have a 55 gallon tank with 3 oscars in it. It had a parrotfish in it also up until this morning. The parrot appeared to have fungus on him. Here's my story:

The tank was doing great. I had the 3 oscars, a parrot, a clown knife, and a large silver dollar. They all got along well and the tank seemed to be thriving. The oscars, as you know, are very destructive and broke the glass thermometer that I had in the tank. I took out the broken glass and did a water change to vacuum out the small silver balls that are in the bottom of the thermometers. Two days later, my knifefish died. He didn't appear at all to be sick and I wondered if the thermometer had something to do with it. I was told that thermometers no longer contain Mercury and that they contain alcohol. I hoped that the water change and new carbon would remove this. A few days later, my silver dollar appeared to have a few scratches on his side and died that night. Just recently, about 10 days ago, I noticed that my parrot had a few small patches (which later developed into large patches) of white cotton-looking stuff on his side. I then noticed that one of the oscars also has some on him too, although it was not nearly as bad as the parrot. I assumed that this was fungus and began to treat the tank. I used Melafix and Pimafix together with the recommened doses for the full 7 days. I took out the carbon from the filter and waited the outcome. It didn't work. The other oscars look infected (a few small cotton looking spots on them). The parrot got worse and died this morning. I am now worried for my oscars and hope that someone can give me advice on how to treat them. I cannot use a hospital tank because they are too big. I do use salt in my aquarium and replace it when I do water changes (once a week 10%). My parameters are all good, no ammonia, nitrites good, pH 7, temp 78 degrees.
I am just wondering if anyone has any ideas so I don't lose my oscars. I am not sure where this whole episode in my tank has come from and I've never experienced this type of dilemma before. I do feed the oscars feeders, but have decided to stop this in case the disease was brought to my tank from them. I have 6 tanks currently set up ranging from 29 gallons to 90 gallons and no other problems to report. Please help me and give some ideas on what I can do to save these fish.

Hi 2many

Sounds like a columnaris infection is going through your tank. I have a strong belief that such things are easily brought in with feeders. All one needs to do is study the fish closely in those tanks and you'll see a complete pathogenic set of cultures going on in there.

If all you have are the oscars and no other fish like scaleless fish, then you will want to move on to antibiotic.

I would take a two fold approach.

1) Dose the tank with either Maracyn (erythromycin) or another antibiotic such as Furan-2, or Fungus Eliminator. Maracyn-2 is for secondary bacterial infections and won't work for a columnaris infection which is what sounds like you have going on. It can be seen as cottony tufts, scales outlined in white and raised, mouth fungus, body fungus, saddleback lesions, or white filmy lesions around the caudal peduncle area.

2) I would feed the Oscars the new Jungle Anti-Bacteria Medicated Food Pellets. This will prevent secondary infections and aid somewhat in the external infection. You can try this approach alone if you are concerned with adversely affecting your biofilter. Right now it is easiest to find this at Petsmart. Jungle says it will soon be more widely available.

When you say nitrites are good, does this mean they are zero? Only zero is good. If they are even slightly elevated, then your filter isn't handling the load. And, it is quite a load with 3 oscars in a 55 gallon, not to mention the other fish you had. How big are these guys?

One number we need to see is the nitrates. This helps us to see just how well that tank size is handling the load and if your water change regimen matches. For example, ideally you want to be around 20ppm or less. You can really go up to 40ppm without detrimental effects, but 20 is a good target. If you are really up there, like 100ppm or more, this will compromise the fish's immunity. It dilates blood vessels and just contributes to declining health. If you find that they are up, do a 30% water change before medicating, but make sure the water temp does not change by more than 1-1.5F. If it should drop 3-4F or more, you risk bringing on ich. If you raise it by that much, you will likely see the columnaris infection really take off.

Incidentally, columnaris is most virulent at 77F and higher. If your tank is above that temp, you may want to consider lowering it 1F daily until you get to 76F. It won't stop it, but it may slow it slightly.

Salt is good against columnaris.

Last edited by Cory_Di at 26-Jan-2005 10:02