Sick Plecostomus

Question
I have a 55 gal tank, no live plants or sharp objects. In this is my  6 yr old plecostomus, a Pakistani loach, and a number of guppies. I do not feed live food but I do feed a wide variety of commercial foods. I do regular maintenance and cleaning, water quality is good. 2 days ago I noticed small white cotton-like spots on the plec's face around the top of his mouth, cheeks, and top of head. I thought he had maybe gotten too close to the heater and burned himself (though the heater is set on a very low temp) Nonetheless, I disconnected it. I treated the water with Melafix and figured he would show improvement. But today it seems like the spots are getting bigger and he is looking sunk in as if he is not eating. I also noticed spots on some of the guppies which were not there yesterday.I do have 4 other tanks and all are maintained in the same way with plecs in 3 of them and they all seem fine. I looked in my fish health book but none of the pictures and descriptions quite matched. I hope this is enough information and I thank you very much in advance for your time.

Answer
Hi Janet,

White cottony growths are a sign of either fungal or Columnaris infection. It has nothing to do with the heater. In fact, you should definitely put the heater back in, because a drop in temperature will make the fish stressed, and more vulnerable to disease.

If the growths look like 'fur', and have a yellowish or grayish tinge, and extend far out from the body, it's a fungal infection. In that case, change 30% of the water, and treat with a medicine, such as Jungle Lab's Fungus clear, or Pimafix, etc. Fungal infections are extremely easy to treat.

However, fungal infections don't usually spread to other fish. They usually affect stressed or wounded fish.  It's most likely not fungus, but a bacterial infection, of Columnaris bacteria. Fortunately, it's also easy to treat.

Columnaris is characterized by cottony, white growths near the face area, later spreading to the body. this is probably what you have. First, do a 30% water change, and then treat with an anti-bacterial medicine. Since Melafix is not working (most likely because the infection is too serious, or is expired, etc.), treat with a 'heavier' type of anti-bacterial medicine. A combination of Maracyn and/or Maracyn 2 is best. During any treatment, remember to remove the carbon from the filter, as it will remove the medication.

Columnaris will spread faster with high temperatures, while low temperatures won't slow it. Keeping the temperature at 75F is ideal during treatment.

I hope this helps!

Good Luck, and I hope your fish recover!